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The Terrarium: A Thriller
Not yet published
Expected 10 Nov 26A true crime fanatic uncovers a nefarious secret when she takes a peculiar cat-sitting assignment in this spine-tingling suspense novel from the author of Peter Miles Has to Die.
Annie’s life is going nowhere—she’s in her thirties and getting by with cat-sitting jobs. While her clients head off on exotic beach holidays, Annie is left scooping litter and wondering how she ended up as the spectator in other people’s lives. Her one sliver of excitement is Cuppa Crime, a true crime podcast with an active online forum where she obsessively dissects murder mysteries with other fans. That is until a new client, Zoe, reaches out to book Annie’s services.
Zoe is aloof and mysterious, and she seems intent on keeping it that way. She gives Annie access to her glamourous house and handwritten instructions on how to look after her darling cat, Hades—all without meeting, or speaking, in person. Soon into the gig, Annie is vicariously living through the client she’s never met, her imagination running wild with the possibilities of inhabiting another life.
And yet something feels wrong about the house. It’s not just the closed-off room Annie is explicitly forbidden from entering. When odd souvenirs begin to pop up in Zoe’s home—souvenirs that seem connected to ongoing murder investigations—Annie suspects that there may be a more sinister side to her client.
Is it all in Annie’s head, the product of too much true crime and an overactive imagination? Or are her instincts on point? Because the number one rule of Cuppa Crime is "trust your gut." And if Annie’s gut is telling her anything, it’s that her cat-sitting client is a serial killer.
Annie’s life is going nowhere—she’s in her thirties and getting by with cat-sitting jobs. While her clients head off on exotic beach holidays, Annie is left scooping litter and wondering how she ended up as the spectator in other people’s lives. Her one sliver of excitement is Cuppa Crime, a true crime podcast with an active online forum where she obsessively dissects murder mysteries with other fans. That is until a new client, Zoe, reaches out to book Annie’s services.
Zoe is aloof and mysterious, and she seems intent on keeping it that way. She gives Annie access to her glamourous house and handwritten instructions on how to look after her darling cat, Hades—all without meeting, or speaking, in person. Soon into the gig, Annie is vicariously living through the client she’s never met, her imagination running wild with the possibilities of inhabiting another life.
And yet something feels wrong about the house. It’s not just the closed-off room Annie is explicitly forbidden from entering. When odd souvenirs begin to pop up in Zoe’s home—souvenirs that seem connected to ongoing murder investigations—Annie suspects that there may be a more sinister side to her client.
Is it all in Annie’s head, the product of too much true crime and an overactive imagination? Or are her instincts on point? Because the number one rule of Cuppa Crime is "trust your gut." And if Annie’s gut is telling her anything, it’s that her cat-sitting client is a serial killer.
304 pages, Hardcover
Expected publication November 10, 2026
About the author
Katie Collom
2 books62 followersKatie Collom grew up in Mazatlán, Mexico and is a life-long expat and world traveler. She spent four years in Texas and has carried a piece of it with her ever since. Currently, she resides in York, England, with her husband and three cats.
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Displaying 1 - 5 of 5 reviews
June 14, 2026
Annie is a 30-something true-crime junkie, barrista, and cat sitter. When a mysterious, wealthy client named Zoe hires Annie through a cat sitting app, a strange dynamic forms. Zoe only communicates through brief text messages, leaving Annie to wonder who she’s really cat sitting for.
The story features a true-crime backdrop, with mystery and suspense throughout that will keep you fully engaged. The plot prioritizes an unsettling atmosphere where the universe seems to actively push Annie toward danger, but her thoughts and antics will keep you thoroughly entertained.
The heart of this novel lies in its complex, highly entertaining characters:
* Annie: A protagonist with incredibly poor self-regulation skills, a wild imagination, and a flair for the dramatic.
* Zoe: An enigmatic figure who may or may not be executing her own form of dark, altruistic justice.
* Gail and Gary: Podcast hosts who frame the narrative, tracking the life of a cat sitter with a story to tell, but will they get the full story?
This is an absolute MUST-READ for fans of Listen for the Lie (Amy Tintera) and Mad Mabel (Sally Hepworth). It delivers a clever, twisty, psychological ride that will leave you questioning just how far you would go to satisfy your own curiosity.
(I received an Advanced Reader Copy of this book for free, and I am leaving this review voluntarily.)
The story features a true-crime backdrop, with mystery and suspense throughout that will keep you fully engaged. The plot prioritizes an unsettling atmosphere where the universe seems to actively push Annie toward danger, but her thoughts and antics will keep you thoroughly entertained.
The heart of this novel lies in its complex, highly entertaining characters:
* Annie: A protagonist with incredibly poor self-regulation skills, a wild imagination, and a flair for the dramatic.
* Zoe: An enigmatic figure who may or may not be executing her own form of dark, altruistic justice.
* Gail and Gary: Podcast hosts who frame the narrative, tracking the life of a cat sitter with a story to tell, but will they get the full story?
This is an absolute MUST-READ for fans of Listen for the Lie (Amy Tintera) and Mad Mabel (Sally Hepworth). It delivers a clever, twisty, psychological ride that will leave you questioning just how far you would go to satisfy your own curiosity.
(I received an Advanced Reader Copy of this book for free, and I am leaving this review voluntarily.)
Review of advance copy received from NetGalley
Thank you NetGalley and Bantam for the ARC in exchange for an honest review!
“The Terrarium” by Katie Collom is one of those thrillers where you start out thinking, "Wow, this woman makes some questionable life choices," and by the end you're thinking, "Wait... maybe she's actually the most dangerous person in the room."
And honestly? I had a great time watching the chaos unfold.
The story follows Annie, a thirty-something barista, professional cat sitter, true crime addict, and world-class snoop. Annie's life isn't exactly going according to plan. While everyone else seems to be moving forward, she's spending her days feeding other people's cats, listening to murder podcasts, and spiraling into increasingly questionable decisions.
Naturally, when a wealthy new client named Zoe hires her to cat sit, Annie immediately becomes obsessed.
To be fair, Zoe isn't exactly helping matters. She communicates only through brief text messages, never seems to appear in person, lives in a gorgeous house, and leaves Annie one very specific instruction: don't go into a certain room.
If you've ever read a thriller before, you already know how well that's going to go.
One of my favorite things about this book is Annie herself. She is not your typical thriller protagonist. She's morally gray from the very beginning. She steals small items from clients. She snoops through personal belongings. She inserts herself into situations that are none of her business. She becomes obsessed with people way too quickly. In short, she is exactly the last person who should be trusted with someone's house keys.
Which makes her incredibly entertaining to follow.
Annie also has one of the most unique narrative voices I've read in a while. Throughout the book, she imagines true crime podcast hosts commenting on her life like she's already the subject of a future murder documentary. Between chapters, there are even podcast transcript interludes discussing Annie and the events of the story. At first, I wasn't entirely sure whether these segments were real, imagined, or somewhere in between, and honestly, that uncertainty only added to the fun.
Because the more time you spend with Annie, the more you start realizing something isn't quite right.
The book is definitely a slow burn. If you're looking for constant action and nonstop twists, this probably isn't the thriller for you. Much of the story focuses on Annie's grief, loneliness, unhealthy obsessions, and growing fixation on Zoe. The suspense comes less from big shocking moments and more from the creeping realization that both Annie and Zoe are hiding things.
And wow, does Annie become fixated on Zoe.
After noticing a few strange items around the house that seem connected to murder investigations, Annie becomes completely convinced that Zoe is a serial killer. Does she have proof? Not really. Does that stop her? Absolutely not.
At several points, Annie feels less like an amateur detective and more like a stalker who accidentally wandered into a thriller.
What I found fascinating is that the book constantly shifts your perception of both women. At first, Zoe seems like the obvious threat. She's mysterious, secretive, and potentially dangerous. Annie, meanwhile, appears awkward, impulsive, and emotionally messy.
Then the story keeps peeling back layers.
And suddenly you're not so sure who should be worrying about whom.
The character work is honestly the strongest part of the novel. Annie's obsession with becoming like certain people, her inability to regulate her impulses, and her tendency to create toxic attachments make her feel both deeply flawed and strangely compelling. She's not always likable, but she's almost impossible to look away from.
The mystery itself unfolds gradually, with a few reveals that I genuinely didn't see coming and others that I suspected earlier. The truth behind Zoe's forbidden room ended up being partly surprising and partly exactly what I thought it would be. But Annie's reaction to those revelations? Completely unhinged in the best possible way.
By the final act, the tension ramps up significantly as everyone's secrets start colliding. The climax brings together the various storylines in a satisfying way, complete with a memorable death and enough suspense to keep me fully invested.
Also—and this is important—the cat survives.
In fact, Hades the cat may be the most emotionally stable character in the entire book.
The ending wraps up the central mystery while leaving just enough ambiguity to suggest Annie's story isn't necessarily over. And honestly, that's fitting. Annie is the kind of character who feels like she'd find trouble even if trouble actively tried to avoid her.
Overall, “The Terrarium” is a slow-burning psychological thriller packed with true crime obsession, unreliable narration, morally questionable decisions, cat sitting, and two women who are far more alike than either of them would probably like to admit. It's creepy, funny, weirdly charming, and driven by one of the most fascinatingly chaotic protagonists I've read in a while.
If you enjoy unreliable narrators, character-driven suspense, true crime satire, and thrillers where the amateur detective might actually be the biggest red flag in the story, this is definitely worth picking up. Just maybe don't hire Annie to watch your house.
“The Terrarium” by Katie Collom is one of those thrillers where you start out thinking, "Wow, this woman makes some questionable life choices," and by the end you're thinking, "Wait... maybe she's actually the most dangerous person in the room."
And honestly? I had a great time watching the chaos unfold.
The story follows Annie, a thirty-something barista, professional cat sitter, true crime addict, and world-class snoop. Annie's life isn't exactly going according to plan. While everyone else seems to be moving forward, she's spending her days feeding other people's cats, listening to murder podcasts, and spiraling into increasingly questionable decisions.
Naturally, when a wealthy new client named Zoe hires her to cat sit, Annie immediately becomes obsessed.
To be fair, Zoe isn't exactly helping matters. She communicates only through brief text messages, never seems to appear in person, lives in a gorgeous house, and leaves Annie one very specific instruction: don't go into a certain room.
If you've ever read a thriller before, you already know how well that's going to go.
One of my favorite things about this book is Annie herself. She is not your typical thriller protagonist. She's morally gray from the very beginning. She steals small items from clients. She snoops through personal belongings. She inserts herself into situations that are none of her business. She becomes obsessed with people way too quickly. In short, she is exactly the last person who should be trusted with someone's house keys.
Which makes her incredibly entertaining to follow.
Annie also has one of the most unique narrative voices I've read in a while. Throughout the book, she imagines true crime podcast hosts commenting on her life like she's already the subject of a future murder documentary. Between chapters, there are even podcast transcript interludes discussing Annie and the events of the story. At first, I wasn't entirely sure whether these segments were real, imagined, or somewhere in between, and honestly, that uncertainty only added to the fun.
Because the more time you spend with Annie, the more you start realizing something isn't quite right.
The book is definitely a slow burn. If you're looking for constant action and nonstop twists, this probably isn't the thriller for you. Much of the story focuses on Annie's grief, loneliness, unhealthy obsessions, and growing fixation on Zoe. The suspense comes less from big shocking moments and more from the creeping realization that both Annie and Zoe are hiding things.
And wow, does Annie become fixated on Zoe.
After noticing a few strange items around the house that seem connected to murder investigations, Annie becomes completely convinced that Zoe is a serial killer. Does she have proof? Not really. Does that stop her? Absolutely not.
At several points, Annie feels less like an amateur detective and more like a stalker who accidentally wandered into a thriller.
What I found fascinating is that the book constantly shifts your perception of both women. At first, Zoe seems like the obvious threat. She's mysterious, secretive, and potentially dangerous. Annie, meanwhile, appears awkward, impulsive, and emotionally messy.
Then the story keeps peeling back layers.
And suddenly you're not so sure who should be worrying about whom.
The character work is honestly the strongest part of the novel. Annie's obsession with becoming like certain people, her inability to regulate her impulses, and her tendency to create toxic attachments make her feel both deeply flawed and strangely compelling. She's not always likable, but she's almost impossible to look away from.
The mystery itself unfolds gradually, with a few reveals that I genuinely didn't see coming and others that I suspected earlier. The truth behind Zoe's forbidden room ended up being partly surprising and partly exactly what I thought it would be. But Annie's reaction to those revelations? Completely unhinged in the best possible way.
By the final act, the tension ramps up significantly as everyone's secrets start colliding. The climax brings together the various storylines in a satisfying way, complete with a memorable death and enough suspense to keep me fully invested.
Also—and this is important—the cat survives.
In fact, Hades the cat may be the most emotionally stable character in the entire book.
The ending wraps up the central mystery while leaving just enough ambiguity to suggest Annie's story isn't necessarily over. And honestly, that's fitting. Annie is the kind of character who feels like she'd find trouble even if trouble actively tried to avoid her.
Overall, “The Terrarium” is a slow-burning psychological thriller packed with true crime obsession, unreliable narration, morally questionable decisions, cat sitting, and two women who are far more alike than either of them would probably like to admit. It's creepy, funny, weirdly charming, and driven by one of the most fascinatingly chaotic protagonists I've read in a while.
If you enjoy unreliable narrators, character-driven suspense, true crime satire, and thrillers where the amateur detective might actually be the biggest red flag in the story, this is definitely worth picking up. Just maybe don't hire Annie to watch your house.
Review of advance copy received from NetGalley
Thank you to NetGalley and Ballantine Publishing for an advanced copy of this fast-paced, clever thrill ride.
The Terrarium is set up as a true-crime podcast where hosts Gail and Gary take a deep dive into a possible murder mystery on an episode entitled “Did Curiosity Kill the Cat Sitter?” After Annie may have accidentally killed her client’s elderly cat and definitely maced her client’s brother, she is desperate for as much cat-sitting work as possible before her ex-client ruins her career.
Desperation for work and for a human connection entangle Annie in the world of a possible serial killer when she takes on a cat-sitting job for a mysterious client named Zoe. As she becomes more and more enthralled with Zoe’s home and upscale lifestyle, she can’t help but explore parts of the house that have been deemed “off limits.” Annie soon discovers trinkets that are not associated with her client but with missing men. Is Zoe a stone-cold killer or a vigilante seeking justice? Either way, Annie may have found the connection she has been craving…but at what cost?
The Terrarium was a fun ride from beginning to end–I found myself cheering for Annie one minute, and cringing for her the next. The storytelling made me feel like I was listening to a podcast and wanting to shout, “NO, ANNIE! GET OUT OF THERE!” This book gave me darker Finlay Donovan vibes, and I was all in!
The Terrarium is set up as a true-crime podcast where hosts Gail and Gary take a deep dive into a possible murder mystery on an episode entitled “Did Curiosity Kill the Cat Sitter?” After Annie may have accidentally killed her client’s elderly cat and definitely maced her client’s brother, she is desperate for as much cat-sitting work as possible before her ex-client ruins her career.
Desperation for work and for a human connection entangle Annie in the world of a possible serial killer when she takes on a cat-sitting job for a mysterious client named Zoe. As she becomes more and more enthralled with Zoe’s home and upscale lifestyle, she can’t help but explore parts of the house that have been deemed “off limits.” Annie soon discovers trinkets that are not associated with her client but with missing men. Is Zoe a stone-cold killer or a vigilante seeking justice? Either way, Annie may have found the connection she has been craving…but at what cost?
The Terrarium was a fun ride from beginning to end–I found myself cheering for Annie one minute, and cringing for her the next. The storytelling made me feel like I was listening to a podcast and wanting to shout, “NO, ANNIE! GET OUT OF THERE!” This book gave me darker Finlay Donovan vibes, and I was all in!
Review of advance copy received from NetGalley
If you like quirky novels about unstable true crime fanatics, this book might be for you!
Annie's a mid-thirties cat-sitter/barista who's addicted to the podcast Cuppa Crime. Things aren't going well for her until she receives a text from Zoe, who wants to hire her at double her usual rate to look after her cat Hades. She just has to make sure to never ever open the doors to the studio. Instead of seeing this as an odd request or a blood-red flag, Annie exults at the prospect of making more money; maybe she can finally pay her car repair and get her car back!
So Zoe's house is unsettling, as you might expect. Things come and go mysteriously (some also disappear with Annie as "souvenirs") and Annie remains obsessed by what's in that studio. What could Zoe be hiding?
This book didn't quite tickle my fancy. I enjoyed Annie as a character and especially her barista bestie, but Zoe? Eh. I would actually have liked to learn more about her and her motivations. The book would have benefitted from a split narration, with chapters showing her perspective, as well as Annie's. The big reveal is just what you would expect and, thus, a bit of a let-down.
Thanks to Ballantine, via NetGalley, for the ARC!
Annie's a mid-thirties cat-sitter/barista who's addicted to the podcast Cuppa Crime. Things aren't going well for her until she receives a text from Zoe, who wants to hire her at double her usual rate to look after her cat Hades. She just has to make sure to never ever open the doors to the studio. Instead of seeing this as an odd request or a blood-red flag, Annie exults at the prospect of making more money; maybe she can finally pay her car repair and get her car back!
So Zoe's house is unsettling, as you might expect. Things come and go mysteriously (some also disappear with Annie as "souvenirs") and Annie remains obsessed by what's in that studio. What could Zoe be hiding?
This book didn't quite tickle my fancy. I enjoyed Annie as a character and especially her barista bestie, but Zoe? Eh. I would actually have liked to learn more about her and her motivations. The book would have benefitted from a split narration, with chapters showing her perspective, as well as Annie's. The big reveal is just what you would expect and, thus, a bit of a let-down.
Thanks to Ballantine, via NetGalley, for the ARC!
June 30, 2026
I really loved this. It's about a true crime junkie who catsits, and thinks that she may be watching the cat of a murderer. I loved the way it was written and I enjoyed that there was a true crime podcast in between some of the chapters. I thought that there was a lot of twists and I was definitely invested in this main character. She might be one of my favorite MC's this year. Make sure to put this on your TBR - coming November 2026.
Displaying 1 - 5 of 5 reviews