Really enjoyed this one! I’ve been favoring domestic thrillers over crime thrillers lately, but this book definitely has me questioning that decision.

Head Cases introduces the elite FBI Patterns and Recognition (PAR) team, led by the brilliant yet socially isolated Gardner Camden. Tasked with stopping a vigilante targeting serial killers, Camden and his team—a mathematician, a weapons expert, and a computer whiz—race against time to unravel cryptic clues and outwit a killer who’s always one step ahead. Camden’s sharp intellect and awkward charm give serious Spencer Reid vibes, making him an even more compelling protagonist.

Camden’s neurodivergence and strained personal life add depth to his character, while the well-rounded supporting team enhances the story’s dynamic. McMahon delivers fast-paced action, clever twists, and relentless suspense, keeping readers guessing until the end.

Perfect for fans of crime procedurals and psychological puzzles, this gripping read concludes with room for future installments, and I’m already looking forward to seeing where the PAR team goes next.

I would like to thank NetGalley, the publisher, and the author for this ARC in exchange for my honest review.

A number of years ago my son got me hooked on the tv series Criminal Minds which features an elite group of FBI agents in the Behavioral Analysis Unit. Though it occasionally gave me nightmares, I enjoyed discussing the cases and characters with him. When I read the synopsis for HEAD CASES, I was instantly drawn to it thinking it might be a book we could both read, enjoy, and discuss.

HEAD CASES works as a police procedural for the same reasons Criminal Minds works. It features enigmatic characters - both as hunters and the hunted - and delves into the motivation behind twisted criminal behavior. It’s not so much car chases and gun fights as it is head games and psychological maneuvering.

John McMahon gives us the Patterns and Recognition Unit (PAR) which was once held in high esteem, but is now relegated to working behind a desk on cold cases. FBI agent Gardner Camden has a brilliant mind, but lacks the people and political skills necessary to succeed within the agency. When a long presumed dead serial killer turns up as a murder victim and is linked to a pattern of suspicious deaths, Camden and the PAR are pressed into service to hunt a serial killer of serial killers.

McMahon does a terrific job laying out the backstory of the PAR in this first book of a series. The team is comprised of agents all with particular skills. There is no shortage of tension and red herrings as Camden and his team follow the clues in an attempt to find the killer.

The audiobook is expertly narrated by Will Damron who brings depth to his characterization of Camden and the supporting cast.

I’ve pre-ordered a copy to be delivered to my son on release day and look forward to our discussion. I’m already anticipating the next book in the series.

Thank you to NetGalley and Macmillan Audio for the advance copy in exchange for my unbiased review.

This was a fantastically fast paced police procedural. I always forget how much I love police procedurals until I read a really great one like this. From the get go we are trying to figure out the identity of the serial killer who is killing serial killers. Dexter style. That fact alone had me 100% in. The PAR (Patterns and Recognition) Unit has a group of remarkably bright agents who are able to solve cold cases and cases other agents can't solve with their brilliant brains and knack for figuring our difficult puzzles. Agent Camden is placed as Head Investigator on their latest case and I really enjoyed the story from his point of view. I also enjoyed his family/personal story and how it impacted his decisions and career. This story was so fast paced and had me on the edge of my seat towards the end. I loved how I was always wondering who did it, especially when the clues indicated it could be someone in the FBI! The narrator did a fantastic job and did a great job voicing all of the different characters.

Thanks to NetGalley and Macmillan Audio for my ALC of this story which publishes 1/28/25.

The plot of Head Cases, a serial killer who kills serial killers and is being hunted down by the FBIs Patterns & Recognition unit, was intriguing and kept me listening to the audiobook until the end. However, the characters felt shallow and superficial to me.

Turns out it's still illegal to be a serial killer even if you're only killing former serial killers. This clever first in a series book of the PAR Unit (Patterns and Recognitions) of the FBI is set to attempt to find this murderer, regardless of his motives. This interesting grouping brings to mind Slough House, a similar mish-mash of those with a somewhat sordid past in MI-5. Camden is leading this investigation and I like the way his seeming neurodiversity brings much-needed thought processes into the case. This is not a fast-paced, twisty, turny thriller, and I don't think that was its intention. I took it for what it was and enjoyed the reveals all the way to the end.
I also thought the narrator did a good job with multiple characters, but as always a multi-cast for the females and different dialects would have been ideal to me.
Thanks to NetGalley and St. Martin's Press for this ARL. All opinions are mine.

As a Criminal Minds fan, I really enjoyed this read! Agent Camden reminds me of an older Spencer Reid sent to work with the “outcasts” of the FBI. As an analytic genius, he can’t help but see all the facts and let his mind notice every little detail about everything.

This team is put on a case following a serial killer… who kills killers. Camden’s team sets out to take this man down, despite the question that crosses their minds- is this killer doing something good for the world? Until this vigilante, goes too far. Definitely an enjoyable mystery/crime novel!

I came across this one while trolling the reviews of GR friend, Liz. It sounded really good, like my kind of story; about a team of FBI agents, who all have a big black mark on their FBI records and got banished to PAR group as punishment. So, an all-around really fun bunch of folks, who are all wicked smart and kind of funny, that make for a really great read.

There’s the group leader, Frank, who almost had a liaison with a superior’s wife. There’s Gardner, who turned his wife, Anna, in when he found out she was embezzling money. He now shares custody of their daughter, Camila, with his MIL, Rosa, who can’t stand him for what he did to Anna and husband, Saul. Besides being his FIL, Saul was also Gardner’s partner (who Gardner idolized), who had a heart attack and died when Anna was arrested. Yeah, there’s a WHOLE lot of family drama going on there.

There’s also Cassie, the mathematician, who had some “incident” with a superior, and then there’s the weapons expert Jo, aka Shooter. who had some kind of shooting snafu on a case. Lastly, there is Richie, who wasn’t banished to PAR, but actually asked for the assignment straight out of Quantico. Immediately, the rest of the team became suspicious of him. Nobody would ever ask to be a part of PAR,
and that is a whole other story to be revealed later.

Most of the story revolves around PAR investigating a case of a serial killer killing serial killers. Things take a turn for the worse when the killer has info that no one else would have except law enforcement. Then the case gets personal and the killer has info on Gardner that only the FBI has. The end gets kind of crazy and intense and a whole lot bargaining and wrangling, which ends in a lead-in to the next installment. One that I will definitely be looking out for.

The character development on some of the characters was well done, like Gardner and the killer. Would have loved to see more development on the team, especially Cassie and Shooter (love Shooter!), but that was probably by design and McMahon is saving it for the next installment. I REALLY want to know what that “incident” Cassie had with a superior. I have an idea and I really hope I’m not too far off. Anyway, the pacing was steady to fast, the storyline very interesting and the writing was well done. I’m looking at an overall rating of 4.2 that I will be rounding down to a 4star review. I want to thank NetGalley and Macmillan Audio for sending me this eARC in exchange for my honest review.

#NetGalley #MacmillanAudio #HeadCases

Gardner Cameron's head is a fascinating place to be.

Head Cases follows FBI Agent Cameron and his team, as they investigate a serial killer who appears to be taking out other serial killers. As the body count rises, each member of the team showcases their skills and abilities to put together the clues purposely left behind by the killer, and the ones he tries to hide.

Gardner Cameron doesn't miss much. With an eidetic memory, he can recall a fact or moment in time like reaching into a filing cabinet and pulling out a transcript. He is a fantastically written character and it was a refreshing perspective to read from. In my experience, the super smart, "brainy" characters are usually cast in background or supportive roles, and being able to watch the story unfold from behind his eyes made it that much more interesting. (Spencer Reid, anyone?)

The plot bores full speed ahead, with twists lurking around every corner. I raced through this book, trying to piece together the mystery, unable to stop without letting it play out to its explosive conclusion. I will absolutely be tuning in for the next book in this series and waiting very impatiently for its announcement.

Sure to fascinate lovers of shows like Criminal minds, and fans of the 4MK series, don't miss out on this one. It was fantastic on audio! Shoutout to Will Damron for the engaging narration.

Publication date: January 28th, 2025

Thank you to NetGalley and Macmillan Audio for an early copy in exchange for honest review.

This book was enthralling! I binged it in one day after seeing a few 5 star reviews from my friends. It definitely lived up to the hype and I look forward to reading more of this series.

The audiobook narration was very well done and played a significant part in keeping me dialed in.

Thank you to NetGalley and Macmillan Audio for this free audiobook ARC in exchange for my honest review.

I found Head Cases to be an engaging and entertaining audiobook that was easy to follow and enjoyable from start to finish. The story’s premise—an FBI unit solving seemingly unsolvable cases—pulled me in right away. The Patterns and Recognition (PAR) team, with their unique mix of skills and personalities, brought an ensemble dynamic that felt fresh and kept the story moving at a good pace.

Gardner Camden’s character, a puzzle-loving but emotionally distant agent, added an interesting layer to the story. His interactions with the other team members and the personal stakes with his daughter, Camila, gave the plot some depth. I also liked the riddle-laden, high-stakes cat-and-mouse game with the killer, which kept me guessing and invested until the end.

The novel is fairly clean, making it accessible to a wide range of readers, and the narration of the audiobook was smooth and engaging, making it a breeze to listen to. I also appreciated how the book didn’t get bogged down in overly graphic scenes or unnecessary subplots.

Overall, Head Cases is a strong debut, and I’m definitely planning to explore more from John McMahon in the future. If you enjoy thrillers with a smart, quirky team of investigators and a suspenseful storyline, this is a great pick!

This was definitely a good crime thriller/police procedural, I've just realized I think this genre is not my favorite. It was exciting yes but slow at the same time. It was just missing something for me. It was a great story though, great plot and characters. The writing was also superb.

🎧 The narration was good but I did feel like it was very monotone so sometimes it was hard to keep my interest. I still stuck through it as the story was interesting, but not my favorite audio.

I ate this book up! I listened to this in one sitting! It felt like an episode of criminal minds and numbers combined and I loved it so much. I cannot wait until the next book comes out. The twists and turns keep you intrigued and wondering throughout this entire book. The best way I can describe this is a giant game of cat and mouse. Thank you to NetGalley and Macmillan audio for the opportunity to listen to this arc for my honest review.

Though not my usual type of read, I am so glad I requested Head Cases!

It's the kind of audiobook that grabs you and makes you forget everything else. McMahon really grabbed me with his writing and plot, but it was the characters who wouldn't let me go.

At the heart of the story is Gardner Camden, an FBI agent who’s brilliant with puzzles but often misses the human side of the case. Together with his equally endearing yet quirky, talented team, Gardner tackles a chilling case: a serial killer long presumed dead has resurfaced, leaving behind a trail of cryptic clues and riddles, seemingly just for Gardner. As the investigation unfolds, the killer gets eerily closer, putting everyone at risk.

As I said, what makes Head Cases stand out isn’t just the fast-paced mystery—it's the characters. Each agent in the PAR (Patterns and Recognition) unit has a unique skill set and personality that makes them feel like real, fully fleshed-out people. Their dynamics and banter are both fun and endearing, balancing the darker aspects of the case perfectly.

This was the perfect, gripping thriller to listen to on audio. I sped through this one and I think many other people will as well. I'm hoping McMahon turns this into a long series. I'll be listening to each one for sure.

“The expression serial killer is just a convention of man…at the end of the day, every killer is just a human, searching for something.”

Police procedurals are pervasive in the current entertainment sphere. Ones with complex and compelling plots narrow the field. But the ones with incredibly well drawn characters who show us all the in-betweens are rare. It’s no surprise that the film/tv rights have already been sold for this novel and I’m already looking forward to the next in the series!

I’m reluctant to compare Head Cases to the brilliant Slough House book series by Mick Herron, but in this case the correlation is deserved. Just as the MI5 has a niche group of misfits, McMahon has created a similar group within the FBI. The PAR (Patterns And Recognition) unit is comprised of agents, demographically different, who share a lack of adherence to the norms. They are all incredibly talented in ultra specific ways but have run into political roadblocks along their career paths. The group itself (nicknamed The Head Cases) is in danger of being dismantled and the players operating within are in danger…period. As they hunt down a serial killer who is killing infamous serial killers, their skill sets and their vulnerabilities come into focus. Law enforcement and politics combine like oil and water and in this case, create an incendiary device exploding with collateral damage.

Smart themes, snappy dialogue and fresh perspective made this a fabulous one sitting read for me. Bravo Will Damron for bringing these quirky and diverse characters to life!

Thanks to Net Galley, Minotaur Books and Macmillan Audio for the early copy in exchange for my honest review, which will be promoted on my Instagram page @bookshelfbybeckwith, Goodreads, Amazon and Barnes & Noble closer to publication day.

Head Cases is a puzzle you are trying to solve as you read. How can a serial killer who is dead leave his DNA on a murder victim? The PAR (Patterns and Recognition) unit of the FBI is on this case and has an expert in every field that they need to crack the case. Agent Gardner Camden is great at puzzles and putting the pieces all together. They figure out when the murders continue that a serial killer is killing serial killers. Great read for anyone who likes reading about crime and serial killers!

Thank you to NetGalley and Macmillan Audio for the advanced copy of this book.
I loved this book. John McMahon is a new to me author and I am so excited to see this was book #1! The premise of this book was an FBI special unit that was tasked to hunt a serial killer that is killing serial killers. It had everything a thriller/psych thriller/mystery should have. I loved Gardner Camden, the main character and his team, the way that they look and process the clues they come across.. Listening to the audio, the writing was so descriptive it was almost like I was with the team seeing it with my own eyes.
This book is full of unexpected twists and turns that will keep you guessing at every turn. If you're like me and you love a good thriller/psychological thriller, this read will grip your attention and keep you captivated until the very last page!

I really enjoyed listening to this audio! I was a little confused by the plot, there were a lot of characters and things to keep up with. Maybe I will have to do a reread at some point, but I enjoyed the time I spent listening all the same!! Definitely twisty, turny, and thrilling!

Thank you NetGalley and Macmillan Audio for sending this book for review consideration. All opinions are my own.

When the FBI gets a case no one else can solve, they call in the Patterns and Recognition team. The PAR team has a variety of specialized skills, pulled together for their ability to see what other agents may miss. This is a group of misfits who have experienced failures on other team, which has put them in the crosshairs of FBI leadership. Their latest case has also put them in the crosshairs of a serial killer. Will they find the killer before leadership shuts them down?

Acclaimed author John McMahon returns with Head Cases – the debut of the new PAR Unit series. Known for the PT Marsh detective series, McMahon latest work has already been optioned by HBO Max before it’s even hit shelves! This is a book about leaning into strengths others may see as weaknesses, but also a realistic look at how loss impacts each of us differently. With mystery, drama, and relatable characters, this book will keep you engaged and entertained the entire way.

I give Head Cases 5 out of 5 stars. I connected with the main character and got pulled into the storyline from page one. I enjoyed the mystery and will admit I didn’t figure out who the criminal was until the author revealed in later in the book! The author crafts scenes with detail and authenticity that bring them to life off the page – I can understand why this was picked up for the screen! The only holdback I had on giving this a perfect 5.0 rating was a few slight errors when referencing locations in Georgia. In one specific example, the author references a location of “south of Atlanta”. Having lived south of Atlanta all of my life, that typically references locations that are still north of Macon – the location in the book was several hours further south nearly to the Florida border.

If you love Karen Slaughter’s Will Trent series, Marc Cameron’s Arliss Cutter series, or the Jack Ryan books by Tom Clancy, you will love this book! It would also be a great choice for a mystery or crime book club – there is so much to unpack about the main character and the crimes. With gun violence, death, and serious injury, I would direct this to readers over 16.

I have recently been watching the Netflix “Mindhunter” about the early days of serial killer profiling in the FBI, so I was immediately drawn to this novel when read the description on NetGalley. I love police and military thrillers and this was right up my alley. Head Cases will release on January 28th – you can preorder you copy in our Bookshop.org store today!

I am excited to share I recently discovered a new, exciting author and thriller by John McMahon that will keep readers on the edge of their seats.

A gripping new thriller by John McMahon that promises to keep readers on the edge of their seats! This intense narrative delves into the chilling world of serial killers through the lens of a uniquely formidable group within the FBI. When a wave of serial killers turns up dead, the elite Patterns and Recognition (PAR) Team springs into action. Led by the brilliant Gardner Camden, they race against time to track down a new killer while being taunted by a mysterious vigilante.

Determined to halt the escalating violence and bring their prime suspect to justice, Camden and his team must stay one step ahead in a complex game of cat and mouse.

McMahon crafts an action-packed tale that grabs your attention from the first page. Those acquainted with Gardner Camden's thinking know he's a master at piecing together puzzles, often spotting details that elude everyone else. Some might see his talent as a hint of autism or savant-like abilities, but his unique perspective is invaluable in the high-stakes world of the FBI.

Typically called in when other teams falter, the PAR Team excels at solving cold cases. But this time, they're thrust into a fiery scenario where discretion is paramount. Camden— is faced with the challenges of untangling a web of deception while confronting the shocking resurgence of a supposedly dead serial killer. The dynamics of Camden's personal life add another layer of complexity to the narrative. His struggles to maintain a relationship with his estranged wife and daughter, who struggle to understand his quirks, and the dedication he places on his job further humanize him while serving to illustrate the psychological toll of his profession and the societal disconnect he faces due to his analytical disposition.

As bodies of serial killers pile up, the team grows increasingly uneasy about the possibility of a vigilante on the loose—someone bent on cleaning up the remnants of the FBI's past failures. The stakes couldn't be higher, with rumours swirling about the PAR Team's imminent disbandment. When the elusive killer begins to toy with Camden, leaving behind cryptic clues, the countdown begins to unveil a foe determined to make their mark and ensure these brutal killings don’t go ignored. Gardner Camden may finally have met his match unless he can uncover the missing link.

John McMahon delivers an electrifying thriller that keeps you guessing at every turn. The narrative unfolds rapidly, weaving together a complex tapestry of clues that propel the story forward with relentless momentum. As the tension builds, readers find themselves piecing together the mysteries, only to be met with unexpected twists that heighten the intrigue. Key characters are richly developed throughout, each offering tantalizing glimpses into their pasts, leaving ample room for future exploration.

With constant revelations and surprises, the plot maintains a sense of ongoing mystery that gradually unravels hidden truths. I eagerly await John McMahon’s next installment featuring Gardner Camden, whose enigmatic character has much more to reveal.

This book is a must-read if you love well-paced, non-stop action, solving puzzles, and unravelling mysteries with compelling, realistic, richly developed characters, and you enjoy crime procedurals— prepare yourself for a rollercoaster ride of unexpected twists and turns that will keep you guessing at every turn. For those with a flair for tracking serial killers, this exhilarating read will surely grip your attention and keep you captivated until the very last page!


I had a wonderfully immersive reading experience as I alternated between the audiobook and my Kindle. Will Damron's narration truly stood out; it was fantastic. He brought the character of Camden to life in a way that felt incredibly authentic and relatable. It was as if he had stepped right into Camden's shoes, allowing every moment of the story to resonate deeply with me.<br/><br /><b>I would also like to express my gratitude to St. Martin's Press/Minotaur Books and Macmillan Audio for providing a copy of the e-arc and a copy of the ALC through NetGalley in exchange for honest feedback. All opinions expressed are my own.
The expected release date is January 28, 2025

“Head Cases” by John McMahon is about a unit within the FBI called PAR (pattern and recognition). On this case, they are searching for a serial killer who is out to killing other serial killers in a gruesome manner. DNA has shown that the killer who was presumed dead a long time ago, is alive and leaving a trail of riddles and signs that will lead the PAR Unit to him.

Liking the characters was so easy for me and I was fully invested in their success and downfalls. This is a police procedural, special unit story and a thriller/mystery all rolled into one. It is fascinating in its construction, the weaving of the characters, the perfect red herrings to the end and entertaining the whole time. I definitely recommend Head Case. I can’t wait to read the second book in the series in early 2026.

Thank you to NetGalley, the author, John Mc Mahon, and the publisher St. Martin’s Press/ Minotaur Books for the opportunity to read and review an advanced reader's copy of Head Case.