Neurodivergent detective characters have become a trope recently, but author McMahon doesn’t make his Special Agent Gardner Camden a gimmick. It makes sense that the FBI would have a Patterns and Recognition Unit and that its staff would have unusual skills, including eidetic memory and an outstanding ability to amass, analyze, and interpret information—like Gardner has.

The PAR team is called in when a serial killer they thought long dead is found murdered in a way that mimics how he treated his victims. As they investigate this murder, more murders of serial killers occur and the team is off at a breakneck pace to try to crack the case and bring down the “Mad Dog” killer, as they nickname him.

Gardner has a great backstory, and the members of his team are appealing too, though less fleshed-out in this first book. The book blends clues and solutions well with thrilling action and suspense, making it tough to put down, especially once you reach the second half.

John McMahon is an author new to me, but after reading this standout thriller, I want to look for his three P. T. Marsh books, and I look forward to his second Gardner Camden/PAR novel.

Head Casss follows the main character, Gardner Camden a member of a specialized unit of the FBI. The Patterns and Recognitions (PAR) unit is group of FBI unique agents with advanced expertise. The group of agents follow a serial killer hunting serial killers who taunts the agents. Leaving clues along the way. The plot was a complex game of cat and mouse between the FBI and the subject. Head Cases is intriguing and will hook the reader from the beginning.

Gardner Camden is a member of the Patterns and Recognitions (PAR) unit, a specialized group of FBI agents with advanced analytical and technical expertise. Camden, who is neuro-divergent, is a brilliant investigator but struggles with social interactions. When a serial killer believed to have died in a house fire seven years ago in Florida is found murdered in Texas, the PAR unit is called in. As they begin their investigation, another serial killer is found dead. Camden is appointed to lead the team once it becomes evident that the murderer has acquired inside information about the serial killers and is taunting the FBI. Could the murderer be an FBI insider acting as a vigilante? 

Head Cases is the first book in John McMahon's new series featuring the fictional FBI PAR unit, a team of "oddballs, rejects, and weirdos," as they are often referred to behind their backs. The plot is cleverly crafted, with the murderer leaving clues that only brilliant minds can decipher. I thoroughly enjoyed the cat-and-mouse action. Perfect for fans of CBS-TV's Criminal Minds. Sign me up for Book 2. 

(Note - I was initially on the fence in reading this book but because I had downloaded The Minotaur Sampler, Volume 13, I was able to read the first few chapters, and it was all I needed to choose this book. Very glad I did.)

Rated 4.25 stars.

This was such a good police procedural. It had engaging characters (loved the MC), it had a twisted, gruesome mystery, it was suspenseful and had a lot of action (perfect for a movie adaptation).

The PAR unit of the FBI (Patterns and Recognition) is a group of outcasts. Every one of them has their own story of why they were assigned to the team. The main character, Gardner Camden, is an analytical genius and can easily solve puzzles. Unfortunately, he doesn't have keen social skills and sees most things as black-and-white... but that just makes him a quirky character that you can easily root for. He does have a soft spot for his 7-year-old daughter Camilla and his mother, who is in an assisted living facility in Texas..

When a man is murdered, he comes up in the FBI database as a serial killer everyone thought was dead. Including Camden, who was the agent chasing him years ago. But now he's dead? Then when another serial killer is found dead, Camden and his team start to see a pattern emerging. The victims are also covered in weird clues. Can Camden and his team solve this one before the killer strikes again?

This book had such a good balance of character development, mystery, suspense and action. It pulls you in and makes you want to keep reading. If this is indeed a series, I'm definitely reading the next one.

I don't usually love police procedurals, but this one struck me as one that I would really enjoy watching as a show or series.

It is a good one for fans of Criminal Minds. The story didn't entirely stand out to me as unique because of how many police procedural dramas I have seen, but I enjoyed the characters and the ride.

Interesting premise - a serial killer targetting serial killers. This has a dry Joe Friday - just the facts feel and I couldn't get into the groove.

Briefing
Case File #001: Gardner Camden and the PAR Unit
Summary:
This book introduces the enigmatic Patterns and Recognition (PAR) unit of the FBI—a misfit team tasked with solving cold cases. When a presumed-dead serial killer is murdered, and similar victims surface, the team finds themselves in a race against a mastermind who is leaving riddles behind.
Operatives:
• Gardner Camden: Code-cracking genius, emotionally distant but fiercely dedicated. His analytical precision is both an asset and a liability.
• PAR Unit:
• A sniper with a sharp aim and sharper wit.
• A mathematician who sees patterns in chaos.
• A tech whiz who uncovers truths in data.
• A career agent holding the team together under mounting pressure.
Mission Notes:
• Strengths: Riveting plot, cleverly designed puzzles, and a cast as flawed as they are brilliant.
• Challenges: Themes of justice and morality demand readers question their own sense of right and wrong.
• Outcome: An electrifying debut that leaves the door wide open for more cases in thus new series!
Status:
Head Cases is an unmissable first book in what promises to be a thrilling series. Recommended for those who like their mysteries twisted and their protagonists even more so.
Next Steps:
Secure a copy (comes out 1/28/25) and prepare to lose yourself in this web of intrigue.

<i>Thank you to Netgalley and St. Martin's Press | Minotaur Books for the free digital ARC provided in exchange for an honest review.</i>

This book was a propulsive, action-packed adventure. FBI Agent Gardner Camden is a brilliant, quirky detective (a la TV faves like Will Trent, Monk, Columbo... the list goes on). He's eccentric, but self-aware and trying to fit in. I appreciated the care McMahon took in crafting this main character, but also the care he took in creating a supporting cast that makes space for Camden's eccentricities.

While I anticipated many of the twists, I remained engaged in the story and enjoyed the inevitable reveals.

My biggest issues with the book--and these might be due to the ARC and have been addressed in the final version going to print--are SPOILER ALERT:
<spoiler>Camden says "Shooter and I boarded the plane in El Paso" but earlier in the book he said Richie would be going to Texas with him. Was it a simple typo or was there a significant rewrite and the name wasn't updated accordingly? There were also timing inconsistencies: In chapter 4 McMahon said it was "Forty-three degrees at 5:52 a.m." yet in the same chapter notes that "Even at two in the morning, Frank didn't have a curl out of place." And later in the book, Banning's car was shot and disabled in a shootout, but Camden says they just cleaned it off and drove out in it.<end of spoiler>

Given I read an ARC, I'm making an allowance for these errors. However, if I read a final copy and these appeared, it would frustrate me enough to abandon the series (and perhaps DNF the book) altogether.

I want more!

I loved Gardner Camden, our main character. He’s smart, quirky, and stands out as unique in this oversaturated thriller genre.

The murder mystery is complex and keeps a steady pace throughout. The story is well plotted and easy to follow, but there are lots of pieces and you need to pay attention in order to put together the clues.

I alternated between listening to the audiobook and reading my Kindle copy. Will Damron does a fantastic job with the narration. He fully inhabited Camden’s character in a way that felt honest and real.

I’m so excited that HEAD CASES is the first in a series!

*Thanks to Macmillan Audio for the free audiobook download, and to Minotaur books for the free eARC, provided via NetGalley!*

A book about serial killers with a main character who has difficulty with social situations and an eidetic memory? Sign me up! I started out listening to this book but then wanted to finish it sooner so got out my kindle and finished it up in a couple hours.
This book follows the PAR team at the FBI. A rag tag group of misfits as they race to solve a case that they can’t get ahead on.
I honestly loved every minute of it! Can’t wait to read the next one.
I received an ARC of this title, all opinions are my own.

The head cases are a group of FBI agents that specialize in Patterns and Recognition (PAR)
When Gardner Camden, one of the PAR unit, is called to a crime scene, he finds out that the deceased man is a serial killer that he found at a crime scene seven years ago. Now he’s on the hunt for the serial killer that kills serial killers.

This book was narrated by Will Damron who did so well 👏🏻 the story immediately sucked me in, and I had a great time listening / picking up my e-arc at times I couldn’t listen.

This one is for fans of David Ellis and James Patterson! I love a good police procedural with quirky characters and this one delivered.

Thanks so much to NetGalley, St Martin’s Press for my ARC and Macmillan Audio for my ALC.

Pub date 01.28.25

LOVED LOVED LOVED!!!! And am so excited that there will be at least one more book in this new series!!
McMahon's writing is exceptional and these characters he's created for this series, the "misfits" of PAR unit, are so amazingly relatable that I fell in love with all of them, especially Agent Gardner Camden. Loved getting into his head and reading how he thinks and reacts to things.. Loved the storyline, the twists.. I just could not get enough!! Bravo John McMahon! I'd give it more than 5 stars if I could!!

I was intrigued by the premise and as a Criminal Minds fan, thought this sounded up my alley. Unfortunately the execution didn’t work for me and I decided to DNF. Thank you to the publisher, Netgalley and Macmillan audio for the free ebook and audiobook to review.

Head Cases was a really solid read. It hooked me from the first few pages. 100% recommend if you’re a fan of Mind Hunter! Same overall vibe, really enjoyed it.

This thriller, while initially slow to ignite, ultimately delivers a compelling and unique premise. The concept of serial killers being hunted down by a mysterious force offers a refreshing twist on the traditional cat-and-mouse chase. The pace picks up significantly around the 50-page mark, captivating the reader with a series of intriguing events.

I particularly appreciated the insights into the inner workings of the FBI, providing a realistic and engaging glimpse into their investigative processes. The author's attention to detail, both in character development and procedural accuracy, added depth and credibility to the narrative.

Though the story could have benefited from a more polished edit, the overall impact remains strong. I highly recommend this book to fellow thriller enthusiasts, particularly those seeking a unique and thought-provoking take on the genre.

An engaging and promising thriller about a group of misfit FBI agents whose strength lies in patterns and puzzles. The main character, neurodivergent Gardner Camden, is looking into the murder of a serial killer who was thought to have died years earlier. As other serial killers turn up dead, Camden is dealing with both personal and work issues while racing to stop the killer. The book was fast-paced and short, which left little room for character development but kept me turning the pages. I look forward to future books featuring Camden and his team. Thank you to NetGalley and St. Martin's Press | Minotaur Books for a digital review copy.

This is an excellent police procedural about the Patterns and Recognition (PAR) unit of the FBI, and the agents who comprise the unit. This is the first book of a promising new series. They investigate very difficult cases, and this one is disturbing. This is an intricate story without being overly detailed, and held my attention. The small staff of the PAR have backstories that I want to know more about, and I can’t wait for more books in this series! Highly recommended!

Great premise, and great execution. Neuro-diverse detectives working together to solve cold cases... Gardner is the furthest out on the spectrum, but all of his partners have their own issues. I hope we'll get to know them more intimately in future books.

Thank you to MacMillan Audio (#MacAudio2924) for the ALC and Minotaur and Netgalley for the ARC!

I love police procedural type books, particularly when it involves a specialized unit. PAR (Patterns and Recognition department) was a unique department that I was quite intrigued by. Our MMC was the perfect person to lead it, as he is great with codes, puzzles and riddles. His no-nonsense approach to dealing with everything (except his seven year old daughter), made him, at times, feel like others didn’t know how to take him. But when serial killer from his past is found murdered, Gardner finds himself taking the lead on this case. With the killer leaving clues and puzzles, it’s a race against the clock to figure out who the killer could be.

Hearing Gardner’s perspective as he pondered everyday things - like if he should make a comment out loud or not - was truly eye opening as well and I love that the author included this! I really appreciated his character and how his mind worked. This appears to be the start of a series and I can’t wait to see what adventures are next.

“Headcases” releases January 28, 2025. This review will be shared to my onstage blog (@books_by_the_bottle) shortly :)

This is a magnificent game of cat and mouse. Members of an FBI task force is searching for a killer of killers in this pulse pounding drama. The author has created some very interesting characters that will stick with the reader long after they have closed the book. The plot is a minefield of twists and turns as clues are uncovered. My favorite scene is the one that sees one of the characters destroying the office. The author paints such a vivid picture that places the reader right in the scene. There is just so much about this book that makes it a very interesting read.