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The Other Sister
Not yet published
Expected 18 Jan 26Celeste left her sister behind. Now she’s coming home…
Dr. Celeste Monroe seems to have the perfect life—a thriving psychology practice, bestselling self-help books, and the respect of her peers.
But when patient Daniel St. Clair begins stalking her and releases doctored recordings of their sessions which go viral, Celeste's career crumbles overnight. As death threats flood in and her reputation disintegrates, she realises that what’s happening in the present may be linked to her own troubled past.
When Celeste was fourteen, her abusive mother was murdered. Celeste testified that her twin sister Leah was the killer and Leah was incarcerated in a mental institution.
Now, under intense scrutiny, Celeste’s past is coming back to haunt her. What really happened the night her mother died? Did Celeste know more than she said? Someone out there seems to think she did and now they’re threatening to destroy her.
As Celeste's world spirals and her memory begins to fracture, she must confront a terrifying question: What if the fugue states she's suffered since childhood have been hiding a truth far darker than she ever imagined?
The Other Sister - the terrifying psychological thriller by the best-selling author of The Stepfather and Not My Mother.
Dr. Celeste Monroe seems to have the perfect life—a thriving psychology practice, bestselling self-help books, and the respect of her peers.
But when patient Daniel St. Clair begins stalking her and releases doctored recordings of their sessions which go viral, Celeste's career crumbles overnight. As death threats flood in and her reputation disintegrates, she realises that what’s happening in the present may be linked to her own troubled past.
When Celeste was fourteen, her abusive mother was murdered. Celeste testified that her twin sister Leah was the killer and Leah was incarcerated in a mental institution.
Now, under intense scrutiny, Celeste’s past is coming back to haunt her. What really happened the night her mother died? Did Celeste know more than she said? Someone out there seems to think she did and now they’re threatening to destroy her.
As Celeste's world spirals and her memory begins to fracture, she must confront a terrifying question: What if the fugue states she's suffered since childhood have been hiding a truth far darker than she ever imagined?
The Other Sister - the terrifying psychological thriller by the best-selling author of The Stepfather and Not My Mother.
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Expected publication January 18, 2026
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Displaying 1 - 15 of 15 reviews
December 14, 2025
The Other Sister by Theo Baxter. Publish date Jan 18, 2026.
This book starts out with a set of twins who were used by their mother as a science experiment through throughout their childhood. (Don’t skip the prologue on this book). The author does a really good job at character building and building their backstory as he goes and sets the stage for the twist and turns that come ahead. I read many suspense/thrillers and psychological/thrillers and I felt like he did very good at keeping you guessing at what was happening. It’s a good read with a good and new storyline that stands out from the “same ole” stories we seem to find on repeat. I love the way the author chose to take this story. Although there are mixed reviews about the desire to hear more about how the mom experimented on the kids, as you follow the story you realize he couldn’t have told you that entire story without ruining the ending. I think he did a great job in deciding the direction to take this book.
Content rating on this book is great. There is minimal profanity, no sex and nudity, and no smut. Even the violence in this book is minimal without taking away from the story
I give this a solid ⭐️⭐️⭐️⭐️⭐️.
I received a complimentary digital ARC of this book via NetGalley. Thank you to Inkubator Books Publishing and the author, for the opportunity to read and review this title prior to publication. As always, the opinions expressed in this review are my own.
This book starts out with a set of twins who were used by their mother as a science experiment through throughout their childhood. (Don’t skip the prologue on this book). The author does a really good job at character building and building their backstory as he goes and sets the stage for the twist and turns that come ahead. I read many suspense/thrillers and psychological/thrillers and I felt like he did very good at keeping you guessing at what was happening. It’s a good read with a good and new storyline that stands out from the “same ole” stories we seem to find on repeat. I love the way the author chose to take this story. Although there are mixed reviews about the desire to hear more about how the mom experimented on the kids, as you follow the story you realize he couldn’t have told you that entire story without ruining the ending. I think he did a great job in deciding the direction to take this book.
Content rating on this book is great. There is minimal profanity, no sex and nudity, and no smut. Even the violence in this book is minimal without taking away from the story
I give this a solid ⭐️⭐️⭐️⭐️⭐️.
I received a complimentary digital ARC of this book via NetGalley. Thank you to Inkubator Books Publishing and the author, for the opportunity to read and review this title prior to publication. As always, the opinions expressed in this review are my own.
Review of advance copy
I wish more of the girls story with their mom and what experiments they were out through was part of the book.
I became predictable to me and I found myself just wanting the at story to be over. .. seemed like a long read as I want totally into it.
Sad as he is a good author.
Thanks to the author the publisher and Netgalley for a early release of this email
I became predictable to me and I found myself just wanting the at story to be over. .. seemed like a long read as I want totally into it.
Sad as he is a good author.
Thanks to the author the publisher and Netgalley for a early release of this email
Review of advance copy received from Netgalley
The Other Sister is a tense, twist-filled psychological thriller that delivers plenty of compulsive moments, but it doesn’t entirely live up to its intriguing premise. Theo Baxter sets up a compelling foundation with fractured family dynamics, buried secrets, and a protagonist who constantly feels on the edge of unraveling. The atmosphere is moody and suspenseful, and the book moves at a brisk pace that keeps you turning pages.
Where the novel shines is in its setup. Baxter is skilled at planting doubt and creating an undercurrent of unease. The early chapters raise sharp questions about what is real, who can be trusted, and how far someone will go to protect the past. For readers who enjoy psychological tension and unreliable characters, the opening half is especially strong.
However, the story loses some of its power as it progresses. Certain twists feel telegraphed, and a few character motivations seem thin or inconsistent once the big reveals arrive. The final act delivers answers, but not always with the emotional weight the buildup promises. The pacing also becomes uneven, with some scenes rushing by while others linger longer than necessary.
Despite these shortcomings, The Other Sister remains an engaging read with enough suspense to satisfy fans of domestic thrillers. It’s not as tight or surprising as it could be, but it offers a solid, entertaining experience.
Where the novel shines is in its setup. Baxter is skilled at planting doubt and creating an undercurrent of unease. The early chapters raise sharp questions about what is real, who can be trusted, and how far someone will go to protect the past. For readers who enjoy psychological tension and unreliable characters, the opening half is especially strong.
However, the story loses some of its power as it progresses. Certain twists feel telegraphed, and a few character motivations seem thin or inconsistent once the big reveals arrive. The final act delivers answers, but not always with the emotional weight the buildup promises. The pacing also becomes uneven, with some scenes rushing by while others linger longer than necessary.
Despite these shortcomings, The Other Sister remains an engaging read with enough suspense to satisfy fans of domestic thrillers. It’s not as tight or surprising as it could be, but it offers a solid, entertaining experience.
Review of advance copy received from Netgalley
The Other Sister is a taut, unsettling psychological thriller that grips you from the first page and refuses to let go. Theo Baxter crafts a story that is as much about memory and trauma as it is about obsession and betrayal, pulling the reader into the fractured world of Dr. Celeste Monroe.
Celeste seems to have it all—a thriving psychology practice, bestselling books, and professional respect—until her life implodes when a patient stalks her and doctored recordings destroy her reputation. What makes the novel so compelling is the way Baxter ties this present-day unravelling to Celeste’s troubled past: the murder of her abusive mother, her testimony against her twin sister Leah, and the lingering fugue states that may conceal darker truths than she dares admit.
The tension builds beautifully, with each chapter peeling back layers of Celeste’s psyche. The novel asks chilling questions about trust, perception, and the reliability of memory. Is Celeste a victim of manipulation, or has she been hiding something all along? Baxter’s prose keeps the reader guessing, balancing sharp suspense with emotional depth.
The Other Sister is a dark, twist-filled thriller perfect for fans of psychological suspense. It’s haunting, atmospheric, and deeply human—a story about sisters, secrets, and the terrifying possibility that the past is never truly buried.
with thanks to Theo Baxter, the publisher and netgalley for the ARC
Celeste seems to have it all—a thriving psychology practice, bestselling books, and professional respect—until her life implodes when a patient stalks her and doctored recordings destroy her reputation. What makes the novel so compelling is the way Baxter ties this present-day unravelling to Celeste’s troubled past: the murder of her abusive mother, her testimony against her twin sister Leah, and the lingering fugue states that may conceal darker truths than she dares admit.
The tension builds beautifully, with each chapter peeling back layers of Celeste’s psyche. The novel asks chilling questions about trust, perception, and the reliability of memory. Is Celeste a victim of manipulation, or has she been hiding something all along? Baxter’s prose keeps the reader guessing, balancing sharp suspense with emotional depth.
The Other Sister is a dark, twist-filled thriller perfect for fans of psychological suspense. It’s haunting, atmospheric, and deeply human—a story about sisters, secrets, and the terrifying possibility that the past is never truly buried.
with thanks to Theo Baxter, the publisher and netgalley for the ARC
Review of advance copy received from Netgalley
⭐️⭐️⭐️ (3/5)
The Other Sister by Theo Baxter, publish date 1/18/2026.
This was an engaging read that kept me interested from start to finish, and I appreciated the overall concept and pacing. The story had a strong setup and enough tension throughout to make me want to keep turning the pages.
That said, the ending felt somewhat anticlimactic compared to the buildup. I found myself wishing there had been more exploration of the experiments that were referenced throughout the book - they felt like such an important element of the story, and I would have loved deeper insight into what actually happened. Incorporating flashbacks or more detailed scenes from those moments could have made the narrative even more gripping and emotionally impactful.
Overall, this is a solid thriller with an intriguing premise, but I think it could have reached another level with a stronger payoff and more depth around the story’s central mystery.
Thank you to NetGalley and the publisher for the advance digital copy in exchange for an honest review.
The Other Sister by Theo Baxter, publish date 1/18/2026.
This was an engaging read that kept me interested from start to finish, and I appreciated the overall concept and pacing. The story had a strong setup and enough tension throughout to make me want to keep turning the pages.
That said, the ending felt somewhat anticlimactic compared to the buildup. I found myself wishing there had been more exploration of the experiments that were referenced throughout the book - they felt like such an important element of the story, and I would have loved deeper insight into what actually happened. Incorporating flashbacks or more detailed scenes from those moments could have made the narrative even more gripping and emotionally impactful.
Overall, this is a solid thriller with an intriguing premise, but I think it could have reached another level with a stronger payoff and more depth around the story’s central mystery.
Thank you to NetGalley and the publisher for the advance digital copy in exchange for an honest review.
Review of advance copy received from Netgalley
The Other Sister
Theo Baxter
pub. 01.18.26
⭐⭐⭐⭐
Twins Celeste and Leah were born to be experiments for their psychologist mother, raised to compete, resent, and react. After years of being weaponized against each other, Leah snaps and kills their mother. Leah is locked away, while Celeste grows up to become a respected psychologist with a book detailing her traumatic childhood. But when a patient becomes obsessed with Celeste, her carefully built life begins to unravel.
This was my second Theo Baxter book this year (The Other Family was one of my first reads of 2025), and I really enjoyed both. Theo Baxter excels at character building , or in this case slowly destroying them. The story starts strong and moves fast, keeping me hooked, though the ending felt a bit milder. Some twists were predictable, but others definitely caught me off guard.
A fast-paced psychological thriller and a solid 4-star read. Thank you NetGalley and Inkubator Books for the ARC.
Theo Baxter
pub. 01.18.26
⭐⭐⭐⭐
Twins Celeste and Leah were born to be experiments for their psychologist mother, raised to compete, resent, and react. After years of being weaponized against each other, Leah snaps and kills their mother. Leah is locked away, while Celeste grows up to become a respected psychologist with a book detailing her traumatic childhood. But when a patient becomes obsessed with Celeste, her carefully built life begins to unravel.
This was my second Theo Baxter book this year (The Other Family was one of my first reads of 2025), and I really enjoyed both. Theo Baxter excels at character building , or in this case slowly destroying them. The story starts strong and moves fast, keeping me hooked, though the ending felt a bit milder. Some twists were predictable, but others definitely caught me off guard.
A fast-paced psychological thriller and a solid 4-star read. Thank you NetGalley and Inkubator Books for the ARC.
December 28, 2025
I received an advance copy of The Other Sister via NetGalley from Inkubator Books for my honest review.
The opening half of the book is strong — it immediately pulled me in with a fast pace and an interesting setup. The first-person perspective highlights Celeste’s personality and gives a strong sense of who she is.
In the second half, however, I found myself questioning Celeste’s decision-making. This may have been purposeful, suggesting a deterioration of her mental state, but it didn’t fully align with what I enjoyed about her in the first half. The pacing also suffered at times, with some scenes dragging unnecessarily. Also, one key plot development was a bit confusing once important information is only revealed a few chapters later. This left me wondering why simpler, more obvious steps weren’t taken sooner.
Overall, it’s a solid read for fans of psychological thrillers.
The opening half of the book is strong — it immediately pulled me in with a fast pace and an interesting setup. The first-person perspective highlights Celeste’s personality and gives a strong sense of who she is.
In the second half, however, I found myself questioning Celeste’s decision-making. This may have been purposeful, suggesting a deterioration of her mental state, but it didn’t fully align with what I enjoyed about her in the first half. The pacing also suffered at times, with some scenes dragging unnecessarily. Also, one key plot development was a bit confusing once important information is only revealed a few chapters later. This left me wondering why simpler, more obvious steps weren’t taken sooner.
Overall, it’s a solid read for fans of psychological thrillers.
December 30, 2025
Looking for a bonkers, nonstop thriller? The Other Sister is it, the plot here is CRAZY, and the twists are nearly nonstop. Following the Celeste, whose psychologist mother experimented (yes, seriously!) on her and her twin sister, we pick up with Celeste as a well adjusted adult, who’s careful daily routine is thrown off when she meets a new patient, who is not what he seems.
The story picks up pace almost immediately and doesn’t slow down, this was a quick and entertaining read. My main quibble is that the writing feels a bit emotionless, this could be a creative choice, but sometimes the muted reactions of the narrator stretched credibility.
Overall, if you like thrillers, and you love crazy plot twists, this is one to pick up. Thank you to NetGalley and Inkubator Books for providing an advance copy in exchange for an honest review!
The story picks up pace almost immediately and doesn’t slow down, this was a quick and entertaining read. My main quibble is that the writing feels a bit emotionless, this could be a creative choice, but sometimes the muted reactions of the narrator stretched credibility.
Overall, if you like thrillers, and you love crazy plot twists, this is one to pick up. Thank you to NetGalley and Inkubator Books for providing an advance copy in exchange for an honest review!
December 7, 2025
Title: The Other Sister
Author: Theo Baxter
Rating: ⭐️⭐️⭐️
Publication Date: January 18, 2026
This book is one of the only psychological thrillers that I've read that really focuses on "psychological" things.
I really wish the book had gone into more detail regarding the "experiments" that were performed on Celeste and her sister. That would have really added a little bit of "ooommpph" to the story. Shoot, an entire book about their childhood would be amazing!
Many of the events that occurred were predictable. Even though it was predictable, it's still worth your time to grab a copy and settle in.
Thank you to NetGalley for the opportunity to read this ARC in exchange for my honest opinion/review.
Author: Theo Baxter
Rating: ⭐️⭐️⭐️
Publication Date: January 18, 2026
This book is one of the only psychological thrillers that I've read that really focuses on "psychological" things.
I really wish the book had gone into more detail regarding the "experiments" that were performed on Celeste and her sister. That would have really added a little bit of "ooommpph" to the story. Shoot, an entire book about their childhood would be amazing!
Many of the events that occurred were predictable. Even though it was predictable, it's still worth your time to grab a copy and settle in.
Thank you to NetGalley for the opportunity to read this ARC in exchange for my honest opinion/review.
Review of advance copy received from Netgalley
Celeste may look like she has her life together, but she has survived many childhood traumas and now uses her own survival strategies to help others in her psychology practice. Unfortunately, her life is turned upside down when a patient begins stalking her and then attempts to destroy her career. Now Celeste is confronted with her past as she attempts to save her future.
The Other Sister is a stand-alone mystery with a few twists and turns to keep the reader interested. Baxter has created a story that is close enough to be believable that I began to wonder if this could happen to me. A good read for all mystery fans.
The Other Sister is a stand-alone mystery with a few twists and turns to keep the reader interested. Baxter has created a story that is close enough to be believable that I began to wonder if this could happen to me. A good read for all mystery fans.
Review of advance copy received from Netgalley
Yikes—the mental health rep was all over the place with this one. Cringy to read, and I did not particularly like or connect with any of the characters. While I assume that is by design, it didn’t create an addicting reading experience. The build up was great, but I was bored the second half of the book. Not a psychological thriller I would recommend.
Thank you to Theo Baxter and Inkubator Books for the gifted NetGalley ARC in exchange for my honest review.
Thank you to Theo Baxter and Inkubator Books for the gifted NetGalley ARC in exchange for my honest review.
December 10, 2025
The Other Sister: Theo Baxter
rating: 3 stars
I am a fan of psychological thrillers. This book was a good read although I wish it would have included more of a back story on the sisters. A tad predictable but still enjoyable. If you are a fan of thrillers, worth a read.
Thank you to Net Galley for the chance to read this ARC in exchange for my review.
rating: 3 stars
I am a fan of psychological thrillers. This book was a good read although I wish it would have included more of a back story on the sisters. A tad predictable but still enjoyable. If you are a fan of thrillers, worth a read.
Thank you to Net Galley for the chance to read this ARC in exchange for my review.
Review of advance copy
Celeste is a psychiatrist with a strange past. Her sister was in a mental institution and she feels so guilty because maybe she could have stopped it. Her career is booming until it’s not, everything seems to be falling apart and it could be her twin causing it all.
I received a free copy of this book via Booksprout and am voluntarily leaving a review.
I received a free copy of this book via Booksprout and am voluntarily leaving a review.
Review of advance copy
3.5 🌟
December 11, 2025
This is the second book I have read by Theo Baxter and I loved it! The line between imagination and stark reality is perfectly blurred. Who’s telling the truth and who’s the biggest threat?
Displaying 1 - 15 of 15 reviews