The Stepsister's Secret

by Karen King

She’s family now. But can I trust her?

When my stepsister Alison moves in to look after my mother, everyone in my family is grateful. Alison’s a nurse, and she says she just wants to help. But I don’t trust her.

Years ago, when Alison and I were the same age as my own son Isaac, I made a terrible mistake that tore Alison’s world apart. I hoped she didn’t realise, but the look in her icy blue eyes tells she knows exactly what I did.

I’m certain she’s responsible for my mother getting weaker. I don’t like the way she’s pushing me out, isolating me… and getting way too close to my husband, Nick.

I’m watching her. And I’ll do anything to keep my family safe. But I have no idea just how much danger we’re in…

A totally unputdownable, twisty story of family secrets that have deadly consequences. Perfect for fans of Shari Lapena, Freida McFadden, and Daniel Hurst.

What readers are saying about The Stepsister's Secret:

‘Wow!… utterly GRIPPING! 👌👌👌… drew me in from the very beginning… a rating of a whopping ⭐10! ⭐. Deffo a MUST-READ… I loved this book! I couldn't put it down.’ NetGalley reviewer, ⭐⭐⭐⭐⭐

‘I was hooked from the first page! This book had it all. Suspense, drama, family tension, paranoia it was all bursting out the pages. When I went to bed I was dreaming about it… I screamed at a bit! … Highly highly recommend!’ NetGalley reviewer, ⭐⭐⭐⭐⭐

‘Blown away… I could not turn the pages fast enough.’ Goodreads reviewer, ⭐⭐⭐⭐⭐

‘A brilliant and gripping read which I finished in one sitting.’ Goodreads reviewer, ⭐⭐⭐⭐⭐

‘Had me hooked from the first chapter!… I highly recommend!’ Goodreads reviewer, ⭐⭐⭐⭐

‘Such an addictive twisty thriller… hooked me from the start… bingeable.’ Goodreads reviewer, ⭐⭐⭐

Genres: Audiobook

332 pages, Kindle Edition

First published February 16, 2026

About the author

Karen King is an Amazon international bestselling author of psychological suspense and women's fiction.

Her 8th psychological suspense novel, The Stepsister's Secret, was published on 16th February 2026 by Bookouture and her third 'golden years' novel, Growing Old Disgracefully, will be published by Boldwood on 24th April 2026. This is her 14th woman's fiction novel.

Karen has also had 120 children’s books, two young adult novels, and several short stories for women’s magazines published. Her early writing career was spent working on various teenage and children's magazines.

Her suspense novels The Mother in Law, The Perfect Stepmother and The Stranger in my Bed and her women's fiction novels, The Old Gals' Bucket List, The Runaway Wives and The Cornish Hotel by the Sea all became International Amazon bestsellers.

Reviews

[Keri Stone · Rating 5 out of 5]

Lizzie is happily married with two children. She’s had a rough time with grief and anxiety, but her life is going well; she enjoys her online tutoring job and her Mum lives close enough to walk to her house. After a health issue, her Mum and boyfriend have moved rather quickly to getting married, but Lizzie is happy for her mom.

The wedding day starts out fine, but then her new stepdad’s daughter arrives, and Lizzie recognizes her. Lizzie had been present with Alison, her brother and mom when a tragedy occurred. Lizzie was traumatized by the event, but later she gained more information that made her feel responsible. She has carried this secret and grief for many years… but Alison doesn’t recognize her so maybe her secret is safe.

Her mom has an accident, and rather than healing and getting better, she seems to be getting weaker every day. And Lizzie feels pushed out, just as her husband Nick seems to be acting strange. Then strange things occur at Lizzie’s house.

Everyone has secrets, but who is behind these acts? And can Lizzie figure things out and save her family? There are lots of fun twists that will keep you guessing. Imogen Church narrates this audiobook and overall dies a good job. 4-1/2 stars rounded to 5.

I received this advanced copy from NetGalley and want to thank them, the author and publisher. Releasing on the 16th, so hope more of you check it out. My comments are always my own 😊

[BookishKB]

✨The Stepsister’s Secret✨

Full ARC Review to come. Thank you to Bookouture Audio and NetGalley for the advanced listening copy.

🎧 Narration Style: Solo (Imogen Church)
📅 Pub Date: February 16, 2026

[Bridget Sadenwater · Rating 5 out of 5]

The Stepsister’s Secret is a twisty, addictive thriller that I thoroughly enjoyed. Lizzie and Nick appear to have a happy, settled life with their children, and when Lizzie’s widowed mother becomes engaged to George, everything seems positive—he appears to be a perfect match for her. But once George’s children are introduced, the story takes a darker turn as connections from the past begin to surface.

What really stood out to me was how the clues were revealed slowly and deliberately. Each piece of information builds on the last, keeping the tension high, and I did not see the final twist coming. The pacing and suspense made this a hard book to put down.

I don’t want to give anything away, but if you’re a fan of Freida McFadden-style psychological thrillers, this is absolutely a must-read. A strong 4.5 stars, rounded up to 5.

[Lu thrillskillsandchills · Rating 4 out of 5]

This was such an easy, twisty domestic thriller to fly through.

I picked it up thinking I’d read a few chapters before bed — and suddenly I was halfway through. I finished it in two sittings because the pacing makes it incredibly readable without feeling rushed.

The story is told through multiple POVs — Lizzie, her stepsister Alison, her mum Judith, her husband Nick, and an unknown voice — which adds depth and tension throughout. Each perspective subtly shifts what you think you know.

At the centre is a childhood incident that Lizzie believes tore Alison’s world apart. When Alison moves in to care for Judith, old guilt resurfaces and suspicion starts to build. Is Alison manipulating things? Is Lizzie projecting her own fear? Or is someone else entirely pulling strings?

I did guess the main twist before the reveal, but that didn’t take away from my enjoyment. Watching how it unfolded — and seeing how the different perspectives slotted together — was still satisfying.

A solid 4⭐️ domestic suspense with layered family dynamics and a steady build of paranoia.

[Corinne’s Chapter Chatter · Rating 4 out of 5]

This one took me by surprise! I loved how layered the thriller was, with multiple subplots that converged seamlessly by the end. In my opinion, the book really has two main twists. The first centers on discovering what happened to Allison’s mother years ago—and Lizzie’s (the FMC’s) connection to it.

Lizzie met Allison and her mother on an elementary school field trip, and something occurred that ultimately led to the mother’s death. Lizzie has blamed herself ever since, and the first part of the book dangles this secret for just a bit too long. Adding to the tension, Lizzie doesn’t even know if Allison remembers her at all, while strange and unsettling things begin happening to Lizzie’s own mother—now under Allison’s care after suffering a fall.

All of these layers mostly work well together to keep the reader flipping pages… or in my case, keeping the audio moving along. While I did find the story fairly predictable, it was still enjoyable and engaging from start to finish.

The audiobook narration by Imogen Church was top-notch. Honestly, it was her name alone that made me request this on NetGalley—she’s always such a treat to listen to. Her lovely British-accented vocals offer subtle but distinct differences between characters, making it easy to follow who’s speaking. Listening to her feels like getting a warm hug… that slowly turns a bit sinister and wrong—which is exactly what you want in a thriller.

Final thoughts:
Despite being a bit predictable, this was a thoroughly enjoyable listen. If you’re a thriller lover looking for a layered but easy-to-read domestic suspense story with a strong audiobook performance, this one is well worth your time.

I am thankful to have received a complimentary ALC from Bookouture Audio via NetGalley, which gave me the opportunity to share my voluntary thoughts.

[Kim McFall · Rating 5 out of 5]

I loved this audiobook so much!! It was narrated by my favorite narrator and there are multiple POV’s!

The storyline started out so strong and grabbed my attention from the very beginning. Full of suspense, twists and shocking revelations with each new chapter.

Everyone has a secret, you don’t know who to believe or trust, and it keeps you guessing until the very end.

This is the perfect psychological thriller full of buried secrets, sinister revenge, psychological manipulation & gripping suspense.

⭐️⭐️⭐️⭐️⭐️

[KKEC Reads · Rating 4 out of 5]

The Stepsister’s Secret by Karen King
Holy chaos! This was quite the ride from start to finish. Secrets, twists, turns, and plots for revenge. This took everything, tossed it in the mix, and my goodness… did it ever explode.

I enjoyed how this story was told. Alternating narrators, the timelines, and the mysterious person out for revenge. It was all quite clever. While I guessed who the mysterious person was, there were so many elements I didn’t see coming, and that left my jaw on the floor.

I was drawn into this story, and wanted to fight right beside Lizzie as she tried to protect her beloved mum. To know something isn’t right, but have people insinuating that you’re crazy- I can’t imagine how horribly isolating that had to be.

This had all the highs and lows you want from a well-written thriller. Strong characters, secrets, and someone wants revenge. Brilliantly written, flawlessly delivered, and impossible to put down.

Publication date: February 16, 2026
Publisher: Bookouture

[Kasey Perry · Rating 4 out of 5]

"The Stepsister's Secret" is a fast paced thriller, full of twists and turns. Chapters are short, told from multiple characters' points of view, keeping the reader engaged and the book moving along quickly.

Lizzie suffers from major anxiety due to an incident she witnessed as a child, but she's doing quite well these days, married to Nick and with two children. She has a close relationship to her mother, who is a widow, and is delighted when her mother finds love again in a man named George, though she feels they're maybe moving a bit too quickly. It's at this wedding that she meets her new stepsister, and Lizzie's past and present collide in an unexpected tangle.

I found Lizzie to be a bit naive at times, not connecting dots I felt were a bit obvious. Still, I greatly enjoyed the story and felt all of the "coincidences" tied up very nicely at the end, presenting an overall picture spanning decades.

Thank you to NetGalley and Bookouture Audio for an advanced copy of this book. Karen King is a new to me author, but one I will check out again!

[Pam · Rating 3 out of 5]

This story is about two families with a complicated past who are brought back together when the parents get married. Something happened involving the children when they were younger, and as the families reunite, things start to go wrong and secrets begin to come out.

The plot twist was good and came from one of the people I least expected, although I wasn’t shocked... I listened to the audiobook, and the narrator did a good job. They read with emotion and used different voices for the characters.

However, the story felt a bit slow and repetitive. Lizzy, the main character, is a pity party and sometimes acts a bit childish, which became annoying.

There weren’t any loose ends left unanswered, which is appreciated.

[I received this book from NetGalley and Bookouture in exchange for an honest review. This did not influence my opinion in any way.]

[Kristen · Rating 5 out of 5]

Thank you to NetGalley and the publisher for a copy of this audiobook in exchange for an honest review.

This book was so gripping! I loved the multiple points of view, especially the few chapters from the culprit’s POV as it had me questions who was behind everything throughout the book. I enjoyed the way in which the book had the reader questioning Lizzy and her sanity throughout the whole book through her actions. I really enjoyed this book and did not want to put it down at all.

[Shawn-Joy Martin · Rating 5 out of 5]

I want to scream about this to everyone I know who reads. THIS BOOK WAS SO GOOD!

She’s family now. But can I trust her?

The twists and turns and suspense were so good. Imogen Church was amazing at narrating this one.

[Lana · Rating 4 out of 5]

*ARC review*

This was my first book by this author and it won’t be my last! I had a great time listening to The Stepsister’s Secret. The plot was intriguing from the start and kept me guessing as the drama unfolded. I really enjoyed how the tension built around the family secrets, and the twists made it hard to stop listening. The narration added so much to the experience , it felt natural and really captured the emotions of the characters. A thoroughly enjoyable and suspenseful read!

[Leah M · Rating 4 out of 5]

Thank you to NetGalley and Bookouture Audio for providing me with an ARC of this audiobook in exchange for an honest review.

Karen King is a new-to-me author, and I was looking forward to checking this one out. I wasn’t sure which way this would go for me, since it’s compared to books by Shari Lapena (love her writing) and Freida McFadden (not an author I read anymore since seeing her harmful and inaccurate mental health rep). I was hoping it would be as enjoyable as Lapena’s books are, even if it requires a little extra suspension of disbelief.

The story seemed pretty straightforward initially. Everyone seems to have secrets in this family, and I was thrilled about it. I love a suspense novel that is full of hidden secrets that are bound to come out at the worst possible time. There are multiple POV characters, including Alison, Lizzie, Nick, and Lizzie’s mother, and it seemed like a typical, predictable plot.

However, it becomes clear that in addition to keeping huge secrets, not all of these narrators are reliable. Lizzie in particular becomes an unreliable narrator when more about her is revealed. I didn’t love that her mental health becomes a plot point along with her being unreliable, but it was presented relatively decently. She struggles with anxiety throughout the book as well, and she doesn’t always reach for the most helpful coping techniques. One of the techniques was to wear something around her wrist that she can snap when feeling anxious, which is a harm reduction technique commonly used to stop self-harm. However, she does so unconsciously to the point where it causes physical damage to her wrist. When her loved ones see her wearing it, they become more overprotective—viewing it as a sign that her anxiety levels as high and they assume that they need to ‘protect’ her rather than being actively supportive. I mean, I don’t think that it is an intentional response, but family doesn’t always know how to support a person with mental health issues.

Along with nearly everyone in the story walking on eggshells in an effort to manage Lizzie’s anxiety, Alison infantilizes Lizzie’s mother and everyone in the family simply views it as providing care to her stepmother (except for Lizzie). It becomes clear that Alison’s nursing skills are a way of controlling her new stepmother—she decides who can visit, how long they can stay, and what she is capable of handling, furthering the idea that Alison might be doing something to harm her.

The audiobook is narrated by Imogen Church, who does a fantastic job of voicing multiple characters, tones, and even accents. It was a pleasure to listen to her, even if I wasn’t sure about the plot at first. Church makes the fast-paced chapters fly by, and it was an enjoyable experience.

For the first part of the book, things seemed entirely too predictable. There’s a strange connection between Lizzie and Alison, dating back to when they were very young, around the same age as her 7-year-old son. It was a simple mistake with huge consequences, and it changed the course of the life of everyone involved in the story. This is where Lizzie’s crippling anxiety began, and it was surprising to me that no one in her family noticed the drastic change in her and questioned what it was about. But it’s easy for me to say that as a trained mental health counselor, while loved ones do their best with the limited information and supportive skills that they have.

Initially, all of the evidence seem to point very clearly to Alison. Also, Alison doesn’t seem very mentally steady. She resorts to calling her new stepmother ‘Mum’ right away, and then cancels her return flight to Spain, offering to stay with her father and new mum so they can benefit from her training as a nurse. But something isn’t right—Lizzie’s mother has some worrying symptoms as she’s recovering from a fractured ankle. She’s tired all the time and has become especially weak, and has become completely dependent on Alison in the blink of an eye.

Overall, I found that I enjoyed the second half of the book a lot more than the first half. Whenever I read a mystery or suspense novel, I’ve learned that if everything points to one character, they’re usually the one person who isn’t involved at all. So I tried to stay open-minded, and really struggled with figuring out who the villain is. Most of the plot twists in the book were a complete surprise, so that every time I got to feeling like I knew what was going on, King would throw in a major twist that changed the entire direction of my thoughts. The plot twists were done so well, and each one altered the whole trajectory of the story along with my thoughts. Just be warned, this book is like popcorn—a little isn’t enough.

[Louis (audiobookfanatic) · Rating 4 out of 5]

The Stepsister’s Secret is a fast-paced, binge-worthy thriller that you can easily devour in a single sitting. It’s written in a straightforward, gripping style, reminiscent of novels by Freida McFadden and Shari Lapena, filled with jaw-dropping twists, family secrets, and betrayals that keep the tension high from beginning to end!

The story follows Lizzie, a woman with a devoted husband, two children, and a close bond with her widowed mother, who shocks her by announcing a remarriage after a brief romance. At the wedding, Lizzie meets her new stepsister, Alison, a nurse she instantly recognizes from a traumatic childhood incident she has never stopped feeling guilty about. Alison seems not to remember her. When Lizzie’s mother suffers a fall soon after, Alison moves in to care for her, stirring Lizzie’s growing unease. Convinced Alison hasn’t forgotten the past, Lizzie begins to suspect she may be isolating her, harming her mother’s health, and even edging closer to her husband.

What makes this book so compelling are the multiple POVs, including chapters from Lizzie, her mum Judith, her husband Nick, and even the occasional chilling POV from a mysterious voice plotting against Lizzie and her family. Lizzie’s anxious, spiraling inner dialogue and unreliable narration keep the tension simmering throughout. Her history of anxiety and panic attacks means that when she raises concerns about Alison, both Nick and Judith are quick to dismiss them. The lifelong guilt she carries over what happened between her and Alison as children causes her to constantly second-guess herself—sometimes making impulsive choices that only make things worse. Readers may feel frustrated watching her (and others) miss what seems obvious, but that frustration adds to the suspense. As Judith begins to grow mysteriously weaker and more exhausted under Alison’s care, her POV raises serious questions about what’s really happening in the house. Nick’s chapters portray him as a loving, supportive husband at first, but it also becomes clear he‘s keeping secrets, which adds another layer of tension to their fragile marriage. And then there’s Alison, who’s easy to find unlikable and untrustworthy as she comes across as almost too perfect. Her composed, capable attitude makes it difficult to tell whether she’s genuinely caring for Judith or planning something sinister, keeping readers constantly questioning her true intentions!

The fast pacing, combined with short, sharp chapters that often end on cliffhangers, practically forces you to keep turning the pages. The second half is packed with small twists and clever red herrings, and just when you think you’ve worked it all out, the suspicion lands somewhere new. That said, after all the buildup, seasoned thriller readers may find the final twist predictable and the aftermath a little too neatly tied up for those hoping for harsher justice.

Overall, The Stepsister’s Secret is a twisty, addictive domestic thriller that takes readers on a rollercoaster of emotions and keeps them engaged. It’s perfect for anyone who loves psychological suspense, plenty of family drama, unreliable narrators, and stories where everyone seems to be hiding something. If that sounds like your kind of read and you’re looking for a book you can finish in a single day, definitely add this to your list!

[BooklightYCafecito · Rating 4 out of 5]

Primero que nada… gracias to NetGalley and the publisher for the audiobook ARC. All opinions are my own (even the anxious ones).

This was my first Karen King book and let me just say… ma’am?? Why did you stress me out like that?! Like, yo qué te hice??? How did I hurt you?

So we have our amiga Lizzie, whose mom remarries later in life. Aww, qué cute, right? Pero at the wedding Lizzie realizes her new stepsister, Alison, is someone from her past. And not just “oh we had a class together” past. No. A devastating, life-altering, buried-it-deep-and-prayed-it-stayed-there secret kind of past.

Y ese secreto involves Alison’s mother… and Lizzie’s role in her death.

Yeah. We start there. The author really said, “You ready? No you’re not.”

From that moment on, the book is basically one long spiral of:
• Is Alison pretending?
• Is someone messing with Lizzie?
• Or is Lizzie spiraling again?

And here’s the thing… Lizzie is not unreliable in a manipulative way. She’s unreliable in an anxious, trauma-brain, “what if it’s me?” way. La pobre has had breakdowns before. She questions her memory. She questions her reactions. And because she questions herself… I had to question myself too.

I was constantly second-guessing everything. Todo. Totalmente.

Her husband? Suspicious.
Her stepfamily? Side-eye.
Alison? Absolutely terrifying in that calm, maybe-she-knows way.

The author does such a good job blurring what’s real and what might be anxiety-fueled paranoia. I never felt settled. Every time Lizzie got upset because she knew what was going on, I was right there yelling at her: “Tell them! Cuss them out!” Then she didn’t. And then she was wrong. And I was humbled.

Had me wondering if I was crazier than she was.

And the audiobook?? So well done.

The narrator handled multiple POVs clearly, but what really got me was how she captured Lizzie’s unraveling. You could hear the panic building. The doubt. The internal chaos. It made the tension feel personal. And well… if you can get me to yell at a character, then you’ve done your job. Bien hecho.

I finished this in just over 24 hours because I needed answers. Not wanted. Needed. Porque there’s no way I was wrong. So I could not sleep until I knew who was lying.

Turns out… I was indeed wrong. 😑

Overall, this is a fast-paced psychological thriller that thrives on uncertainty and that horrible feeling of not knowing if you can trust your own mind.

If you like:
– anxious, unreliable narrators
– family secrets
– slow-building paranoia
– yelling at fictional characters and being humbled

You’ll enjoy this one.
Release date: February 16, 2026

[Aisha Faisal · Rating 5 out of 5]

My thanks to Bookouture and NetGalley for providing me with an ARC of The Stepsister’s Secret. I really enjoyed this gripping, twisty read and appreciated the opportunity to read and review it early. I flew through The Stepsister’s Secret. This was one of those “I’ll read a few chapters” books that somehow turned into “oops, it’s finished”.

Lizzie seems to have a pretty settled life with her husband Nick and their kids, so when her widowed mum gets engaged, it should be a happy change… right? Yeah, no. Enter George and his adult children, especially Alison, Lizzie’s new stepsister, and the whole vibe shifts fast. There’s history here. Dark history. The kind Lizzie has spent her whole life trying to forget.

What I loved most was how slowly and deliberately everything unfolded. The author doesn’t rush the reveals; instead, the tension keeps tightening. Alison comes across as calm, capable, helpful… almost too perfect. And once Lizzie’s mum starts declining, and Alison steps in to “help,” the atmosphere turns properly claustrophobic. I was constantly questioning whether Lizzie was being paranoid because of her anxiety, or whether something genuinely sinister was going on.

The psychological side of this really worked for me. The guilt Lizzie carries from her childhood, the way old wounds resurface, and that constant feeling that no one quite believes her it all made the story feel so unsettling in the best way. I had my suspicions (obviously), but the book plays with that so well that even when you think you’ve got it figured out, you’re still not totally sure.

Nick deserves a quick shout-out because he was genuinely supportive and grounding a rare thing in domestic thrillers, honestly. His presence made the tension hit harder because there was actually something stable at risk.

By the time the final twist hit, I was fully invested, and yes, it still managed to surprise me. I was genuinely disappointed when it ended, which is always the biggest compliment. A brilliant and gripping read, which I finished in one sitting. Highly recommend.

Dark, twisty, and very addictive, this is a great pick if you enjoy Freida McFadden–style psychological thrillers where family secrets, buried guilt, and quiet revenge simmer just below the surface. Dark, gripping, and quietly unnerving, The Stepsister’s Secret is the kind of book that makes you say “just one more chapter” until suddenly you’re at the end and wishing there was more.

[Athena 💗 · Rating 3 out of 5]

2.5⭐️ rounded up because it was just interesting enough not to DNF and that has to count for something.

If I was to wrap up this book in one word it would be “chaotic”. How is it possible to get secondhand anxiety from a fictional character? Lizzie’s emotions were like a ping pong ball and every chapter her mind would jump from one conclusion to the next. She was constantly pointing a finger at a different character convinced they were the person plotting against her. It was exhausting and left me feeling like I couldn’t catch my breath. It’s almost like it was so overwhelming that it overshadowed everything else in the storyline and made it hard to truly get lost in the story. The constant chaos made this seem like a fast paced story but then I would think about how much of the story had actually progressed and would realize we never actually got further in the story, we just spent chapters going around in circles.

Another thing that left me confused was that the inner monologue from the different characters POVs would constantly contradict itself. The characters would point blank say their motives or their actions in their POV and then by the next chapter, magically the narrative would magically switch directions. It’s impossible to type out examples without giving away spoilers so you’ll just have to trust me on this one or read it for yourself.

The ending was a bit underwhelming and the fact that all 6 chapters lives just happen to intertwine the way they did seemed a bit farfetched. I kept waiting for the axe to drop at the very end with one last plot twist to leave my mind reeling but it never came. The audiobook came to a closing and I was like… wait, seriously? That’s it?

Since I received this as an ALC I will also share my thoughts on the audio production as well. There are multiple POVs both male and female with only one audio narrator for the entire book. It was extremely confusing to follow along since the narrator lacked a broad range of voices. She would also drop character halfway through the dialogue. She would be talking in Nick’s POV voice only to give up mid sentence and start talking in her “Lizzie” voice. It wasn’t the most enjoyable listening experience.

All that being said, it did manage to hold my attention throughout the story, I was just hoping for a little more from it.

Thank you, Bookouture Audio and Karen King for an advanced audio copy of The Stepsister’s Secret, my opinions are my own.

[Barbara Schultz · Rating 3 out of 5]

Title: The Stepsister’s Secret
Author: Karen King
Format: 🎧
Narrator: Imogene Church
Publisher: Bookouture Audio
Genre: Domestic Thriller
Pub Date: February 16, 2026
My Rating: 3.3 Stars
Pages 322

Lizzie and Nick have two young children Grace and Isaac and they are all pleased that Lizzie’s mother Judith who has been a widow for years is getting married to a man named George. The children are excited about getting a grandfather as Nick’s father also died.
However at the wedding when they meet George’s children. Lizzie is surprised when she sees new stepsister, Alison. She remembers her from when they were children and Alison’s mother died from a reaction due to her peanut allergy. Lizzie has believed she was responsible as she had a peanut butter sandwich for lunch and threw the remainder of into Alison’s lunch bag.
Present day Judith fell and needs assistance; Alison is a nurse and volunteers. Lizzie fears her mother is in danger as Alison may want to ‘pay back’ Lizzie for her responsibility in her mother’s death.

Okay Lizzie is a bit over the top with her worries but guilt is a terrible burden and in this case has not gone away.

Things do get bizarre as Lizzie loses all sense of reason.
I kept at it as I was curious. The ending was satisfying.

The Girl Next Door was my first Karen King thriller which I really enjoyed and have been looking forward to reading another of her thrillers.
I guess my expectations were too high as this wasn’t the Wow read I was looking forward to reading. But I will definitely read another of Ms. King’s thrillers..

Want to thank Bookouture Audio for this audiobook.
Publishing Release Date scheduled for February 16,, 2026.

[Sonja Charters · Rating 4 out of 5]

This was my first read by this author but I could tell from the front cover and title, that this was going to be an intriguing psychological thriller.

This started off brilliantly, hooking me in from the first few pages.
After a stressful build up planning her mum's wedding, it's a relief to arrive at the big day and finally enjoy it.
But when Lizzie's new step sister finally makes an appearance, arriving from Spain, she not only recognises her already, but remembers the tragic day they last met.

Not only does this storyline have me hooked, but there are multiple other side stories running throughout that seem to be separate, but as each one unfolds gradually, connections start to appear.

I thought this was such a great plot and even to the end, the way that the different threads wove around and came together, kept me guessing and a little shocked by the final outcome.

However, I really felt that everything was pushing us towards thinking that a specific person was to blame for all the issues occurring - which fair enough, most thrillers tend to do at some point.
But after some time, I had already worked out that this person was clearly being pushed so much that it wasn't going to be them.
Yet, over and over and over again, there's be some other unsubtle push towards this same person looking guilty.

I think I'd have liked to just see some variation of suspects or even some kind of twist that sent us towards someone else, only to come back to the original person maybe.
I don't know, I just felt the constant nudges got to be a little too much.

That said, I did enjoy the writing style on the whole and the storyline was intriguing.
The characters felt believable and I enjoyed the fluctuating dynamics between them all.
If the initial pace had been maintained, that would have just nudged this up another star.

Overall, an enjoyable read and I'd definitely come back to read more from this author again.

[Leanne · Rating 4 out of 5]

The Stepsister’s Secret is a gripping, quietly unnerving domestic thriller that pulls you straight into a world where old wounds never quite heal and family ties can be as dangerous as they are binding. From the moment Alison moves back into the narrator’s life, the tension begins to coil — subtle at first, then tightening with every chapter.

The dynamic between the two women is wonderfully layered. On the surface, Alison is the perfect helper: a nurse, a dutiful daughter‑figure, someone the whole family is grateful for. But beneath that polished exterior lies a shared history marked by a single devastating mistake — one the narrator has spent years trying to bury. The author captures that uneasy blend of guilt, suspicion, and unspoken resentment with real finesse.
As the mother’s health declines and Alison’s presence becomes increasingly suffocating, the atmosphere shifts into something deliciously claustrophobic. The narrator’s growing paranoia — is Alison isolating her, undermining her, getting too close to her husband? — is handled so well that you’re constantly questioning what’s real and what’s fear talking. It’s exactly the kind of psychological tension that keeps you reading “just one more chapter.”

The story unfolds with sharp pacing, clever twists, and a steady drip of revelations that make you reassess everything you thought you knew. By the time the danger becomes undeniable, the sense of dread is wonderfully intense.

Dark, twisty, and utterly addictive, The Stepsister’s Secret is a perfect pick for fans of Shari Lapena, Freida McFadden, and Daniel Hurst — a domestic thriller where every glance, every silence, and every secret feels like it could be the one that breaks everything apart.

My thanks to Karen King, the publisher and netgalley for the ARC

[Catarina Geirinhas · Rating 3 out of 5]

Thank you Karen King, Bookouture Audio and Netgalley for the ALC!

I just finished The Stepsister’s Secret by Karen King on audio, beautifully narrated by Imogen Church, and I have mixed but very real feelings about this one.

Lizzie and her husband Nick are raising two young children, Grace and Isaac and life feels settled. Lizzie’s mum Judith, widowed for years, is remarrying George and everyone is ready for a fresh start. Until George’s daughter Alison walks into the wedding and Lizzie’s past comes crashing back. As children, Lizzie was present the day Alison’s mother died from a peanut allergy reaction. Lizzie has carried the crushing guilt of believing she played a part in that tragedy after putting the remains of her peanut butter sandwich into Alison’s lunch bag. Seeing Alison again feels like fate knocking with unfinished business.

From there, things unravel in true domestic thriller fashion. Judith has a fall and Alison, now a nurse, steps in to help. Lizzie becomes convinced her mother is in danger. Strange things start happening. Nick begins acting differently. And Lizzie, already fragile from years of anxiety and buried grief, starts to spiral.
I loved the concept. The guilt, the fear of revenge, the question of whether Lizzie is right or losing her grip all made for gripping psychological tension. The alternating perspectives and shifting timelines added layers and there were definitely twists that kept me hooked. Even when I guessed part of what was coming, there were other reveals I did not see at all.

That said, Lizzie can be a bit over the top and at times I found myself frustrated with her reactions. The pacing is more of a slow burn and I was waiting for that huge jaw dropping moment that never quite reached the level I hoped for. The ending, however, was satisfying and tied things together in a way that felt earned.

[Aaron Todd Reads]

📖 Aaron Reads | Book Review

Title: The Stepsister’s Secret
Author: Karen King
Publisher: Bookouture
Do I Recommend?: Yes (for fast domestic thriller fans)

Kindle Unlimited: Yes
Amazon Rating: 4.3 ⭐
Goodreads Rating: 4.15 ⭐
Format: Ebook
ARC: NetGalley

⭐ Star Rating: 3.75/5
🔪 Thrill Rating: 1/5
📄 Pages: 285

Quick Descriptors
• Domestic paranoia
• Family secrets + revenge
• Fast, bingeable chapters
• TW: Mental health exploitation

One-Sentence Take
A tense, slightly predictable, and easy-to-binge domestic thriller about a woman convinced her stepsister is quietly infiltrating her life, and possibly destroying it from the inside. Very addictive pacing! King does a great job of keeping you guessing, even when you’re 99% sure you have it figured out. You’ll find yourself asking… “do I?”

While it’s slightly repetitive and King could trust the reader a bit more to infer, this is still an unputdownable and fun read.

Blurb
When Alison moves in to help care for her ailing mother-in-law, everyone is grateful…except for Lizzie, her new stepsister. Lizzie doesn’t trust Alison. She can’t. Years ago, she made a terrible mistake that tore Alison’s world apart, and now she’s certain Alison knows the truth.

As Alison settles deeper into the household, subtle changes begin to happen. Lizzie feels herself being pushed out, isolated from her husband and family, and increasingly convinced Alison is manipulating everything around her. But paranoia and guilt blur together, and it becomes harder to tell what’s real, what’s imagined, and who is actually in control.

Told through mounting suspicion and buried family secrets, The Stepsister’s Secret is a quick, bingeable domestic suspense read filled with tension, mistrust, and the lingering consequences of past mistakes.

[Shelly Hammond · Rating 5 out of 5]

I really enjoyed this book a lot. This is the first book I have read by this author and I am 100% positive that this will not be the last one I read by her. This book keeps you hooked from the very start.
Lizzie's mom is getting married to a wonderful man named George. She's so happy for her mom and everything is going splendidly until she meets George's daughter, Allison. This isn't the first time she's been around Allison. Soon, Allison is moving in as her mother's nurse when she falls and breaks her foot the night of the wedding. Allison becomes quite bossy taking away her mother's phone, telling LIzzie when she can and can't visit her, and dictating everything. Everyone seems to trust Allison but Lizzie. Lizzie sees her mom growing weaker and weaker not stronger. You see, LIzzie has a little secret about Allison. A secret she's been carrying with her for years and that she worries is coming back to bite her.
I really don't want to tell you too much about this book which is why that bit is little choppy up there. This book unfolds nicely as you read and keeps you guessing. I'm not the best at figuring books out and this one had me accusing everyone of everything at one point or another. I think I figured a portion of it out at around 50% but even so, I wasn't entirely sure about that until the end of the book! A lot happens and a lot isn't what you think it is. I really loved the edge of your seat style of this book that kept me fixated on the story until the very end.
I was so lucky to have been able to listen to the audio of this book, Imogen Church is the narrator and she is one of my all time favorite narrators so I really enjoyed listening to this. I highly recommend it!

[Els · Rating 5 out of 5]

When, as a child, you witness a tragic event, you carry it with you for years—especially when you come to believe that you were responsible for the tragedy.

You were a child. Yes, that’s true, and deep down you know it was never your intention and that it was an innocent mistake. But that doesn’t change the outcome.

Years later, you are confronted with the event all over again when you come face to face with one of the key people involved back then. You fear the worst, yet you still hope you weren’t recognized. Sadly, you were—and now you’re convinced that revenge is lurking just around the corner.

You want to intervene, but you’re on your own. No one believes what you’re saying and they think you’ve slipped back into your old habits…

My focus immediately fell on the most obvious person. Of course, that would be too good to be true, and more often than not this is a smokescreen carefully set up by the author. But perhaps this time the obvious choice is the right one—and maybe it’s precisely that doubt that’s being planted.

Who knows? I certainly won’t say, because I don’t want to deprive anyone of a fantastic book by giving too much away. 🙂

I found the book smoothly written and suspenseful. I was genuinely disappointed when it ended, which tells you everything—you only feel that way when a book is really good.

Sometimes people do things for you, or for others, with the very best intentions—but sometimes they’re after something entirely different…

For me, this book is definitely a recommendation and well worth five stars.

Thank you

[Akku · Rating 4 out of 5]

• 𝐑𝐚𝐭𝐢𝐧𝐠 - 4✨

• 𝐑𝐞𝐥𝐞𝐚𝐬𝐞 𝐃𝐚𝐭𝐞 - February 16, 2026

• 𝐓𝐫𝐨𝐩𝐞𝐬 -
- domestic psychological thriller
- family secrets
- stepsister drama
- unreliable narrator
- slow-burn suspense

• 𝐌𝐲 𝐓𝐡𝐨𝐮𝐠𝐡𝐭𝐬
Lizzie has spent her whole life carrying guilt from a childhood tragedy she can never escape. Now married and trying to live a quiet, settled life, everything changes when her mother remarries and her stepsister Alison enters their world. Alison is calm, helpful, and almost too perfect. A nurse. A caregiver. Someone everyone instantly trusts.
But Lizzie cannot shake the feeling that Alison is hiding something. Old wounds start reopening, tensions quietly build, and the house slowly fills with unease. As her mother’s health declines and Alison becomes more involved, Lizzie’s anxiety grows stronger. The past and present begin to blur, making it hard to tell what is real and what is fear.
This book is a slow-burning psychological thriller that creeps under my skin rather than rushing at me. The author does a great job of creating an unsettling atmosphere where nothing feels completely safe. The family dynamics are messy, emotional, and painfully realistic. I loved how the story keeps me unsure about everyone’s intentions.
The pacing is steady, the writing is smooth, and the tension quietly tightens with every chapter. While I guessed parts of the direction, the journey itself kept me invested. It is dark, twisty, and emotionally heavy in the best way.
Thank you so much Bookouture for the ARC! 💕

[Cassia · Rating 4 out of 5]

3.5 stars rounded up for goodreads!

The Step Sister’s Secret is perfect for readers who love fast, twisty domestic thrillers—especially fans of Frieda McFadden. This is a story that wastes no time getting started and keeps the pace brisk from the very first chapter. The twists come quickly, and just when you think you’ve figured it out, another turn pulls the rug out from under you.

Karen King’s writing is clean and straightforward, which works well for this kind of book. It isn’t fussy or overly descriptive—just tightly focused on momentum and tension. I flew through it, making this a great palate cleanser if you’re in the mood for an easy, popcorn thriller that keeps the pages turning.

My one critique is the ending, which wrapped up a little too neatly for my personal taste. I tend to prefer darker or more messy endings, and this leaned more toward a tidy resolution. That said, if you enjoy thrillers with clear closure, this may actually be a plus.

I listened to the audiobook and want to give a special shout-out to Imogen Church, who is always a standout narrator. She did an excellent job handling the multiple POVs and brought distinct voices and tension to each perspective.

Thank you to NetGalley and the publisher for the advance listening copy. Overall, this was a fun, addictive read/listen that’s ideal for thriller fans looking for something quick and engaging.

[Andria Lambert · Rating 5 out of 5]

This is the first book that I have read by Karen King, though I did just recently buy a few more of her kindle books. I don't like to totally summarize a book because I don't want to give too much away, but in this story, Lizzie's mom gets married and things start to go wrong. Lizzie's mom has an accident and then doesn't seem to recover. Things start to happen that makes Lizzie think something is wrongly going on, and her anxiety ramps up. It seems that Lizzie has a secret from the past and also her husband has a secret from the past. Both those secrets are related to events that have other characters in the story in common. Things are not what they seem. Lizzie feels like something wrong is going on but Lizzie's own husband makes her think that she's imaging things. The story is suspenseful, I couldn't quit reading it to find out what happens. There is a villain or maybe two or maybe three, you don't really know until the end of the book. I enjoyed the twists and turns in the story. The story is fast paced. I would certainly read some more of this author's books. So in summary, there is suspense, drama, tension, deaths from the past and then one in the present and great twists. Thank you Netgalley and Bookouture for the complimentary copy of the story. Thank you Karen King for the story!

[Charlie · Rating 4 out of 5]

Wow! I absolutely loved ‘The Stepsister’s Secret!’ 😍 A twisty, addictive thriller that had me hooked from the first page - I couldn’t put it down! 👩🏼‍🏫 I’d never have found it if it wasn’t for Noelle at Bookouture. The moment I read the blurb, I knew it was right up my street… and I was so right!
Karen has definitely earned a spot on my must-read list! 📚👀

A married couple, Lizzie and Nick, are happy and settled with their two young children. Lizzie’s mum, Judith, randomly meets a man through a Facebook group and their relationship quickly becomes a whirlwind romance. Everything is going great, and before long, they get hitched! 💍💒

All Lizzie wants is for her mum to be happy again after being alone for nine years. 🥰 But when George’s family is introduced, things take an unexpected turn — Lizzie realises she knows George’s daughter, Allison, from when they were kids… 😬

That’s when the story starts to grow darker. The past begins to surface, strange things start happening, and secrets slowly unravel. Is Allison, the new stepsister, responsible? 🤔

From this point on, the twists come thick and fast — and I honestly never saw them coming! 🤯

I would like to say thank you to Karen and Noelle from Bookouture for giving me this opportunity to join the tour. ♥️

[Pages & rituals · Rating 4 out of 5]

ARC Review

When Lizzie’s mother decides to marry George, Lizzie is forced into a new family dynamic she never asked for. When she meets her new stepsister, Alison, she quickly realizes that Alison is not just part of her future but is tied to a very dark secret from Lizzie’s past, a secret they both share.

As the story unfolds, one question lingers. Is Alison here for revenge, or can she be trusted?

This book is packed with secrets, tension, and that constant uneasy feeling that something is not quite right. If you enjoy Freida McFadden–style thrillers, I think you will really like this one. I had my suspicions about what was going on, but even so, the final reveal still managed to shock me.

Nick was easily my favorite character. He was such a devoted husband and genuinely supportive of Lizzie throughout everything. His presence added a sense of stability in a story full of uncertainty.

Overall, this was a very enjoyable read. It was gripping, twisty, and hard to put down. I definitely recommend it if you are in the mood for a suspenseful domestic thriller full of secrets and surprises.

[Jennifer TW · Rating 5 out of 5]

A woman riddled with anxiety. Her mother, widowed and set to remarry. A new stepsister who seems intent on embedding herself into their lives.
Lizzie, a mother of two is married to Nick. She lost her father who died in a work accident when she was young and Nick delivered the sad news. Lizzie suffers with chronic anxiety triggered by an incident in her childhood. A tragedy she has convinced herself she is responsible for. Her beloved widowed Mum, Judith, meets and marries George, himself a widow, and soon Lizzie finds herself with a new extended family. But George and his adult children seem intent on embedding themselves very quickly and when Judith takes a funny turn, injuring herself in the process, new stepsister Alison volunteers herself to take care of Judith much to Lizzie’s dismay. But the thing is, Lizzie knows who Alison really is. And she’s worried that there are dark motives at play.
A brilliant and gripping read which i finished in one sitting. Highly recommend . Huge thanks to the author & publisher for an ARC in exchange for an honest review