Gardner Camden, an FBI agent on the PAR (Patterns and Recognition) team, is part of a group of skilled but reprimanded agents. Despite their past wrongdoings, they’re known for solving cases that stump others.

The team is called in when a serial killer, supposedly killed in a fire years ago by Camden, is found dead. Soon, another serial killer turns up dead, and the team realizes this murderer knows more about the FBI than any civilian should.

How will the team protect each other and their families? Who is the next target?

Binge alert! I need more. My mind was constantly racing with possible scenarios. The PAR team’s flaws and strengths jump off the page in such a brilliant way.

There are no stereotypical heroes here—these are underdogs I wanted to root for and understand, with excellent character development. The descriptions were top-notch, making you feel like you’re running alongside the team.

The plot unfolded brilliantly, with perfect pacing. I can easily see this being adapted for the screen. I’m already looking forward to what’s next for the PAR team—just what I need, another series to add to my TBR!

Thank you NetGalley and Minotaur Books for this ARC!

I really tried to make it through this book, but it was just simply too gruesome for me. The characters did seem interesting, but I couldn't get past the graphic nature, which I'm sure was likely required in some way, but I couldn't stomach it. What I did read of the novel, it seemed well paced and the characters unique and interesting.

John McMahon’s "Head Cases" launches an electrifying series that pits an enigmatic FBI unit against a serial killer with a chilling agenda.

The Patterns and Recognitions Unit—led by the sharp but socially inept Special Agent Gardner Camden and rounded out by math-savvy Cassie Pardo and rookie Richie Brancato—is tasked with solving a macabre puzzle. The discovery of Ross Tignon’s mutilated corpse, marked with the chilling resurgence of a man presumed dead, is only the beginning. When another infamous killer, Barry Fisher, meets a gruesome end shortly after his parole, it becomes clear that the FBI is up against a predator targeting serial killers in a twisted crusade of vigilante justice.

The plot masterfully ratchets up tension with every turn, from cryptic clues and taunting phone calls to the antagonist’s unsettling omniscience within FBI systems. McMahon crafts a deadly game of cat and mouse between Camden—whose razor-sharp analytical skills are matched by his haunted past—and the killer dubbed "Mad Dog." The antagonist’s warped sense of righteousness and cunning make for a chillingly effective foe. Camden’s interactions with his team, especially the contrast between his cerebral methods and his teammates’ more humanistic approaches, add depth to the procedural narrative.

Packed with intrigue, "Head Cases" is a superior thriller that balances razor-edge suspense with dynamic character development. Camden’s intense focus and the emotional stakes tied to Mad Dog’s threats to his loved ones keep the story both cerebral and deeply personal. McMahon’s pacing is relentless, ensuring readers are glued to the page as the revelations unfold. This gripping start to a new series is as chilling as it is satisfying—a must-read for fans of psychological cat-and-mouse thrillers.

This book was a pleasant surprise.
I thoroughly enjoyed it, as it was a quick read and a good time.

What can I say about John McMahon’s Head Cases that hasn’t already been said? I read it in one sitting. This is March and I already know this book is going to be in my Top Ten Books of 2025, probably in my Top Three. I’m going to need more than just the two books under contract in the PAR Unit series. Criminal Minds. Fresh approach to crime fiction. Endearingly quirky characters. Etc., etc.

I rate this 4.75 stars and recommend it to just about everyone. Read the book, y'all; you won't regret it.

Thank you to NetGalley, Minotaur Books, and John McMahon for an advance copy of Head Cases in exchange for an honest review.

Alright my crime fans, did you love Criminal Minds as much as me?? Let me introduce you to your new obsession- THE PAR UNIT!!!

Everything about this book hooked me from the first sentence and didn’t let me go until the end. I want nothing more than another PAR case asap.

If you don’t pick this up now, you’re truly missing out!!!

I personally adore police procedure books that follow a similar path as Criminal Minds, and Law and Order. So when I got accepted for this book I was beyond excited to read my first book by John McMahon.

McMahon uses a neurodivergent character, who is amazing with puzzles, but finds people to be the hardest puzzles. This leads to an interesting dynamic amongst the main characters and those he interacts with such as his daughter. I adored the puzzle aspect and the suspense of what the killer wants from Gardner and his team.

The action in this book was so good and I adored the whole process throughout the novel. If you like thrillers/mysteries with a lot of puzzles and action it would be a great book for someone to pick up.

Thank you for the eARC in exchange for an honest review.

This was an entertaining FBI drama that kept me guessing but for some reason police procedurals are never my favorite. I n this book we follow Gardner Camden the head of PAR patterns and recognition. When a case of serial killer hunting serial killers starts to target him as the one who was on these cases. The first half this book was fast paced,the characters were well fleshed out and the mystery kept me guessing. Toward the back end the pace starts slowing down and I felt like it got a little too slow for me and caused me to lose some interest. This is my first book from this author and a pretty good FBI drama just not for me. I would like to thank NetGalley and the publishers for a chance to read this book for an honest review.

I know the author said this book is part of a 2 book deal, but I’m going to need this to turn into a longer term series. I could see this book as a tv show and I’d be hooked. Gardner Camden leads the PAR group within the FBI and they are chasing someone who is taking out serial killers. The first half had me gripped and I thought I knew where the book would go, when the author decided to go and add an unexpected twist. But the best part were the characters - Camden, Cassie, Shooter, Richie, and Frank. I need more.

FBI Agent Gardner Camden is part of the Patterns and Recognition unit, PAR that tackles challenging cold cases, finding clues others have missed. Each quirky member is gifted in their specialty: a mathematician, a firearms expert, and a computer analyst.

Gardner’s team is called out when DNA of a murder victim matches a serial killer thought to be dead. Soon there’s another murder that seems to be connected and the team is tasked with finding the killer. It quickly becomes apparent this killer knows of the PAR unit and is leaving them clues. With the mistaken identity of the first murder, the FBI wants the case solved quickly and quietly and they want PAR to do it. They hop from scene to scene, as more is revealed, an undercurrent of urgency threaded through the narrative, keeping me on the edge of my seat!

Gardner is an interesting and likeable hero; one I rooted for! His eidetic memory and knack for connecting random details/patterns make him excellent in solving cases, but the ins-and-outs of social interactions seem to escape him. Gardner’s backstory and how he ended up on the team is revealed, but the other’s backstories are only lightly touched on. Callie, a mathematician, Shooter, a firearms expert, Frank their supervisor, and the newbie, Richie. I look forward to getting to know more about them and seeing them settle in together as a team.

Head Cases was a thrilling mystery that had me hooked from the start! I can’t wait for the next one!

I read a lot of thrillers, but it’s been a while since I’ve read a crime novel. And my friends, this is a capital C Crime novel. The murders are gruesome, the detective work is described in minute detail, and there is the constant threat of another body showing up.

I found our protagonist relatable with my own personality quirks, and I felt for his personal struggles on top of his career choices.

I used to be a big Criminal Minds fan, and this book put me right back there. I loved the ending, and I can’t wait for more books in this series!

Thank you to NetGalley and the publisher for the ARC. This review is my own.

Wow this was great!!! This had me tapping my e reader so fast because I had to know!
From the complex mystery to the suspense!!! Top notch!!
One of the best psychological thriller I have read. I highly recommend.

John McMahon’s Head Cases is an electrifying psychological thriller that blends intellectual puzzles with pulse-pounding suspense. FBI Agent Gardner Camden and his elite Patterns and Recognition (PAR) team—tasked with tracking elusive criminals through data analysis—find themselves pulled into a high-stakes chase when a notorious serial killer, presumed dead, resurfaces in a deadly game of cat and mouse.

From the first page, McMahon crafts a gripping narrative, skillfully balancing methodical detective work with moments of intense action. Gardner is a standout protagonist—highly intelligent yet socially awkward, his neurodivergence adding depth to both his investigative prowess and personal struggles. His dynamic with the team, especially as tensions rise and the case becomes personal, is a highlight of the novel.

The mystery itself is layered and complex, filled with clever twists that keep the reader guessing. Just when you think you have the killer figured out, McMahon throws another curveball, making for an unpredictable and thrilling ride. The story’s pacing is expertly handled, building steadily before accelerating into a relentless and satisfying climax.

Fans of Criminal Minds and Mindhunter will find much to love in Head Cases, particularly its cerebral approach to crime-solving and its cast of deeply flawed but compelling characters. With sharp writing, a gripping plot, and an ending that leaves the door open for more, this is a must-read for thriller enthusiasts. I’ll be eagerly awaiting the next installment in the series.

When I first read the synopsis for Head Cases I thought it was going to be very similar to Criminal Minds, but if Reed was the main character (which I would not have been mad about because I love Reed 🫶🏻). However, the more I read it, the more it began to stand out as its own story and not Criminal Minds in a different font. Gardner is similar to Reed on the surface. They both are very logical and very smart, but Gardner definitely has a distinct personality that is different from Reed. Also, probably not fitting for how his character is actually described in the book, but I 100% pictured him looking and sounding like the actor that plays Will Trent.
I liked the plot and was invested in the PAR solving the case. I will say that the outcome was a little predictable, but I still enjoyed it. I am probably most looking forward to seeing if Cassie and Gardner end up getting together in the next book and also seeing Gardner with his daughter more.

FBI agent Gardner Camden belongs to the PAR squad. specializing in unique skills in patterns and recognition, Usually tracking criminals from behind their desks, they find themselves in pursuit of a seriel killer believed to be long dead. The chase is action packed and a step above the standard police procedural with the intelligence of the agents and their investigation. I found the story to be riviting and smart. The characters are multilayered and believable. Head Cases was a riviting and fast read for me and I am hoping that this is the start of a long series. This one hit the bulls eye. Thank you Netgalley and publisher for this very appreciated read in exchange for my honest review.

An agent that has his own personal challenges. An FBI group with troubled careers. A killer who might be cheered by the masses. Let the games begin. 
If you like Criminal Minds, I think you'll really like this book. Each character has their own unique personality that might not allow them to interact with the rest of the world too smoothly. They all have their hang-ups along with their expertise. An imposing team that solves cold cases. But they are drawn into a "hot" case connected to killers who have already met justice. Who is the guy killing killers yet makes it a game directly tied to the main PAR agent? As it gets personal, the tensions rise. 
My main goal in reading stories like this is to figure out the killer before the characters do. I couldn't do it, and that's a good thing. I was along on the ride as the main character analyzed the data and fought with his own internal struggles. I couldn't put the book down. I had to keep reading and see what clue the agent would come up with next and if he could arrive in time to save lives. When a book has me hooked that hard, it's a great read. 
The plot is well planned, but I honestly think it is the main character that had me hooked. He is a serious version of many on TV with their social challenges and brains that aren't wired like the rest of us. I thought that would hinder my enjoyment as I could not relate to them. But the author had a way of not letting this be the focus of the story but an important element. I don't know if I could have worked with the guy, but I really liked him. 
This is a very good read but not for the feint of heart. Body parts will be described as well as some of the actions of the killers. Will keep you on the edge of your seat as you wonder what they'll do next to bring down evil.

I thought this book was good, but unfortunately, I didn't enjoy it as much as I had expected to. I love police procedurals, especially when they involve serial killers, but this one just wasn't as dark as I would have liked, and I had trouble keeping up with the characters at times. I found the pacing in the first half to be slow as well. I did like Gardner and agree with the reviews I've seen comparing him to Reid from Criminal Minds. I would like to learn more background on his character and how he came to work for the FBI.

This is book one in a new series, and I do plan on giving the second book a try when it comes out.

"Our job is to identify peculiarities in cases that have stalled. To solve puzzles and highlight new theories."

An FBI team hunting a serial killer? Yes. I’m ALL in! I love group dynamics with each member bringing their unique skills to the table and HEAD CASES nailed it! Rather than focusing on profiling, this team excels at pattern recognition. No one more so than the team’s quirky yet highly intelligent leader, Gardner Camden. Told entirely from his point of view, John McMahon beautifully and accurately showcases a neurodivergent character that I couldn’t have loved more. He’s diligent, honest and holds a myriad of miscellaneous facts in his head, which he thinks about at random intervals that had me chuckling!

The investigation progressed at a steady pace that increased in tension and sped up to the point where I couldn’t put it down! I became ENTIRELY invested in the characters and particularly attached to Gardner who is resolute in his beliefs of right and wrong and tries his best to navigate relationships based on advice he calls to mind from his beloved mother.

Will Damron is a SUPERB narrator and is now one of my favorites! Not ONE single character sounded the same with voices so distinct (some with accents), that I knew who was speaking immediately. His inflection and delivery of the killer was simultaneously chilling and charismatic. Yet as Gardner’s mother, his tone had a sweet and maternal calming effect. You simply MUST grab the audiobook along with the physical book for the complete experience. One of THE. BEST. audio productions I’ve listened to!

HEAD CASES hit ALL the marks with a diabolical antagonist, a fully fleshed out ensemble cast and an investigation that barreled full steam ahead to an action packed conclusion! I couldn’t get enough of this intense crime thriller with heart and will be first in line for the next installment. In fact, I’m ready for book two. NOW!
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FAVORITE QUOTES:

"He reached out his hand. I stared at it. Over two hundred bacteria thrive on each square inch of our palms. 'Gardner Camden,' I said, shaking. I'm not OCD. I just know things like this."

"I remembered a piece of advice that my mother taught me years ago. To add bits of information at the starts of conversations. To be perceived as more likable. Emotional."

"I nodded, thinking about the two men. They had operated in different decades and in different states. Ages apart, really.
But even though they were unrelated to each other, there was a pattern.
A serial killer was murdering serial killers."
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Potential spoiler content warnings below.


































⚠️Content Warnings: language, dementia, poisoning, mild gore, violence, gun violence, Mention of: gruesome crimes

John McMahon’s Head Cases is a gripping psychological thriller that masterfully blends cerebral puzzles with high-stakes action. Featuring FBI Agent Gardner Camden and his elite Patterns and Recognition (PAR) unit, the novel delves into a chilling murder mystery that resurrects the shadow of a presumed-dead serial killer. As the case unfolds, Camden—a brilliant but socially detached investigator—finds himself in a deadly game of wits, forced to decipher cryptic clues left specifically for him.

McMahon excels at crafting a layered mystery, balancing methodical detective work with moments of nerve-wracking tension. The ensemble cast, from the mathematician to the weapons expert, adds depth and variety to the investigation, making the story feel like a fusion of Mindhunter and Criminal Minds. The team dynamic is a highlight, offering both sharp dialogue and emotional resonance—especially as the case encroaches on their personal lives.

What sets Head Cases apart is McMahon’s ability to intertwine complex psychological profiling with pulse-pounding suspense. The riddles and patterns at the heart of the case aren’t just plot devices; they feel integral to the novel’s DNA, challenging both the characters and the reader. At its core, the book explores the limits of analytical genius when confronted with raw human emotion—a struggle embodied in Gardner’s strained relationship with his young daughter.

With its razor-sharp writing, compelling characters, and relentless pacing, Head Cases is a must-read for fans of cerebral thrillers. McMahon delivers a story that is as intellectually stimulating as it is emotionally charged, proving once again why he’s a standout in the genre.

This was a great cat and mouse thriller. I loved the main character and how his differences were highlighted. I loved the “Criminal Minds” ish way this team worked together. I listened to this as I drove on a long car trip and it kept my attention the whole time. It was intense! Can’t wait to see the next adventure for the PAR team!