The Sleepwalker: Joona Linna Series: #10

by Lars Kepler

MORE THAN 17 MILLION COPIES SOLD WORLDWIDE

The tenth thrilling installment in Lars Kepler's bestselling series— acclaimed for “smart psychological suspense,” “explosive conclusions,” and “gritty portrayals of human evil” (Booklist)—is tense and terrifying.

An emergency call comes in the middle of the night. There is an ongoing burglary at a closed campsite in Bredäng, outside Stockholm. When the police respond to the call, there is a light on in one of the farthest caravans in the otherwise dark area, where the officers are greeted by a horrific sight. The floors, walls, and furniture are completely covered in blood. A person has been killed with an axe and brutally dismembered. In one of the rooms, a young man is sleeping on the floor with a severed arm as his pillow. He is arrested and taken into custody at Kronobergshäktet. There, he is identified as seventeen-year-old Hugo Sand, the son of a famous author.

It turns out that Hugo is suffering from a rare kind of somnambulism, which is triggered by nightmares. He is either the perpetrator or a witness but claims that he remembers nothing from that night.

When Joona Linna is asked to take on the case, he contacts his old friend Erik Marie Bark to use hypnosis in the quest to find out what happened inside the caravan. This is the start of a complicated hunt for a terrifying killer who has just entered an extremely active phase.

Genres: Thriller, Crime, Mystery Thriller, Mystery, Fiction

512 pages, Paperback

Published July 29, 2025

About the author

Lars Kepler is the pseudonym of critically acclaimed husband and wife team Alexander Ahndoril and Alexandra Coelho Ahndoril, authors of the No. 1 internationally bestselling Joona Linna series. With seven installments to date, the series has sold 13 million copies in 40 languages. The Ahndorils were both established writers before they adopted the pen name Lars Kepler, and have each published several acclaimed novels.

Reviews

[Amos · Rating 3 out of 5]

An (at times) effectively suspenseful and tension-steeped chapter in Kepler's hit-or-miss series.

[Kat (Katlovesbooks) Dietrich · Rating 5 out of 5]

The Sleepwalker by Lars Kepler is the 10th In the Detective Joona Linna series.


It's always nice to be caught up with a series, and yet a little disappointed that there are no more to read at this point. 

This was probably one of the best books in this series, although they are all really good.  Be warned that this one in particular is quite gory, and quite dark, which didn't really bother me, but it may some.  As well, there is a lot of sex, which also didn't bother me - except perhaps the fact that Hugo's girlfriend was twice his age.   That may have been fine if he wasn't 17.  There are a number of rather seedy characters in this book, and most of them got what was coming to them, so....  There were also a lot of suspects in this book, and I was lead down the rabbit hole a couple of time...which is fun!

As I always say, this series should be read in order.  You can't appreciate some of the characters unless you know what they have been through -- in this book that would be Joona.  I did miss Saga.

Overall, this was a really well thought-out plot, with a lot of twists, and a lot of suspense, and edge-of-your seat moments.

This Canadian is no longer complaining about the strange place and people names.   I am learning to roll over them, because the plots are so good.  BTW, the translation to English was perfect.

Anyway, I highly recommend the series, so...until next time!


For a more thorough review of this book and others (including the reason I chose to read/review this book, my own synopsis of the book, and its author information), please visit my blog: http://katlovesbooksblog.wordpress.com/

[Danielle-Gemma💜 · Rating 4 out of 5]

Another really brilliant book, I will admit that this book started a little bit slower than normal; but towards the middle I was hooked and I raced through the last 75 pages!

[alyssawhite · Rating 4 out of 5]

The nightmares I will have tonight is insane

[Vicky Hughes · Rating 4 out of 5]

This was such an exciting premise for a book, if you witness a murder while sleepwalking, will you remember it when you wake up? As the deaths mount Jonna Linna has only sleepwalking Hugo as his ‘witness’ to help him put a stop to the vicious murderer. Gruesome, graphic and highly entertaining I thoroughly this latest instalment in the series. Thank you to Netgalley for the advance reader copy.

[Natasha Warren · Rating 5 out of 5]

Love love loved it!!! Another fantastic book in the Joona Lina series.
I’ve followed this series from the beginning and it never disappoints. The was a really good book, fast paced and gory - just how I like it! This has a really clever story line and I would never have guessed who the murderer was.
I would liked to have seen a bit more of Joona and Saga’s lives but I think that’s just because I love them and love their storylines aside from the main mystery in each book.
The only downside for me was the sex scenes, it was a bit much for me but I am a bit of a prude!

A huge 5 stars!!!

Thank you NetGalley for this ARC

[Lance Kirby · Rating 5 out of 5]

Lars Kepler is one of my favourite Scandinavian/nordic authors and the Joona Linna series never disappoints this book and The hypnotist my favourites that’s the reason for the 5 stars so if you haven’t read any of this author or any Scandinavian/nordic author’s I suggest you start reading them you won’t be disappointed

[Dane · Rating 5 out of 5]

I think this is one of their best novels yet. Beware, it's not for the faint of heart.

[Josh Wilson · Rating 2 out of 5]

Was really hooked by this book until the final act. The reveal didn’t hit for me and it all felt a bit rushed and unrealistic! Not Kepler’s best.

[Matt · Rating 5 out of 5]

Lars Kepler returns with the tenth addictive installment of the Joona Linna series. Set in Sweden, it is once again sure to feed my Scandinavian Noir appetite and Kepler delivers like never before. Joona Linna is called in on a troubling investigation, where a teenage boy sleepwalks and may have been an inadvertent witness to a number of violent murders. While Joona tries to peel back the truth, he will have to eke out memories the teenager has, buried deep in the subconscious. This may be a highly troubling case, but Joona Linna has never given up when the truth is out there. Lars Kepler provides a captivating reading experience.

After an emergency call comes in at a campsite outside Stockholm, the authorities rush to the scene. What they discover is a bloody crime scene, where a man has been hacked up with an axe, his limbs removed. Poking around, the police find a young man fast asleep, using one of the limbs as a pillow. He is arrested and Joona Linna is called in to head the investigation, especially as the suspect has no idea what is going on.

Hugo Sand, the son of a famous author, is unsure what happened. He admits to a long history of sleepwalking. Hugo will drift out and do things he cannot remember, which does not bode well for his innocence. However, Joona is not sure they have their killer, as something just does not add up. Joona will have to use his skills to get answers and try to find a killer.

Working with Hugo, Joona insists they use hypnosis to eke out some truths. It will not only help Hugo with his somnambulism, but also identify shards of memories which could point to a suspect. Joona Linna has found a case that not only has his full attention, but as more brutal murders occur, there is no doubt that answers are essential and a brutal killer must be captured. Lars Kepler stuns readers with this addictive thriller.

I have enjoyed the writing of Lars Kepler since the pen name of two popular Swedish authors began collaborating. The work is next level and the attention to detail makes the thrillers all the more impressive. They are dark, yet also filled with clues as the reader loses themselves in the crime and tries to help solve it. The narrative moves along and keeps the reader attentive, as each chapter adds depth and some evidence to the larger story. Characters are well crafted and keep the reader demanding more of them, especially when details are shared to help visualisation. Plot points are, as usual, well placed and forge the larger story. Suspense and surprises are plentiful, in a story that is not diluted by the translation from Swedish. I cannot wait to see what’s next and how Lars Kepler will keep impressing!

Kudos, Lars Kepler, for a series I recommend to anyone who will listen!

Love/hate the review? An ever-growing collection of others appears at:
http://pecheyponderings.wordpress.com/

[Kim · Rating 5 out of 5]

This was another fascinating story in the Joona Linna series of books. Each can easily be read as a standalone thriller but I found my enjoyment increased dramatically after reading them all. After discovering this series with book 8 I then went back and read them all before continuing with the series further, it was worth it!

This book has quite a sedate pace which is a bit of a relief with how gory the crimes are so there is time to recover between each bloodbath. The narration makes it difficult to put down for me as I wanted to know who was behind all of it and to try to understand why it was happening. I admit to feeling a little shock when it was revealed but with that explanation it all made so much sense of even those things I had thought were going to be just background noise to the tale. This book tells a fabulous story from start to finish in a very easy to read style, it was a very enjoyable read.

[Meghan · Rating 4 out of 5]

4.25 I missed Joona and he wasn’t as present in this one

[Tom Wile · Rating 4 out of 5]

Another Swedish thriller. Lars Kepler is the pseudonym of a pair of authors who are also married to each other. The writing is at times graphic and I always wonder which one of them is writing which part. Also what their process is.

Sleepwalker involves a young man accused of a grisly murder while he was sleepwalking. This morphs into a serial murder case and famed detective Joona Lina steps in.

[Sinny · Rating 3 out of 5]

I usually love the Joona Linna books, but this one did not quite do it for me. It wasn’t the page turner I usually find Keplers books to be and the plot twists just didn’t hit as they usually do.

[Jon Rodzik · Rating 3 out of 5]

3.75/ 5 Stars.
I am huge fan of this series and each book has a great pace and is a captivating thriller. This one was solid but not the best in series. Less focus on the lead detective and more focus on secondary characters.

[Jordan · Rating 4 out of 5]

I really enjoyed this book and did not expect Bernard to be the killer! I had pictured him a certain way throughout the book, but when he was finally revealed, I ended up picturing an older version of Bryan Kohberger which made it even creepier 😅

I really like Erik and was glad that he was in this book. I did not miss Saga at all and every time Joona talked about wanting her back, I would say “nooooooo please God no” like Michael Scott. I cannot stand her and am not looking forward to the next book, since it’s heavily implied that she will be back, but will still read it since it’s Lars Kepler!

This book contains even more police incompetency (go figure). Those 2 that got killed were idiots lol. Also, I’m still trying to figure out how the police KNEW THE KILLER WORE A WIG, but never once considered the killer was a man. Like how lol.

I was sad Valeria wasn’t in the book much. I really couldn’t stand her at first, but after what she went through with Pellerina, I really started to like her more.

Overall a great book!

[A. Housewife]

I liked it but I've loved others in this series more. The hypnotism is interesting. I wonder if this exists. I will continue reading this series as long as they keep writing them. I think I liked the mystery part more than others in the series but there was less character development of our main characters so it was less satisfying in that sense

[Amanda Crozier · Rating 5 out of 5]

I had to miss out some of the parts of the book that were too graphic but the storyline made me carry on and it was worth it. I am sure we will have a new chapter of Joona Linna in due course😀

[Kevin Wilmoth · Rating 5 out of 5]

Great read, sorta slow for me at the beginning but the end had an awesome blindside that I didn’t see coming!

[Gail Radka · Rating 5 out of 5]

Brilliant, gory, scary, unthinkable and do readable. Love Joona he needs his partner back though.

[Trav · Rating 3 out of 5]

3.4/5 It’s literally just “the mirror man” again, which was only two books ago…

[Kathi Book · Rating 2 out of 5]

Okay. I’ll admit it, I’m tenacious. I’ve read every book in this series. But this is the absolute end of the road for me! No more.

Giving the series away so that I’m not tempted when the next one comes out….I can’t resist adding to that nice chunk of space on the shelf devoted to an entire series.
Lars Kepler and I are finally parting ways….and freeing up space on that shelf for something more worthy.

There are so many holes in this novel that I wonder if it was even edited at all. Now, normally I would give a translation the benefit of the doubt. But this problem is not unique to just book #10 in this series, all of the books are rife with such holes. And the thing is, these issues always seem as though they would be really easy fixes on the part of the writer/editor. So the fact that the problems continue after 10 books makes me think that both the writing and the editing are just lazy and sloppy.
Sometimes, as I read, I often wondered if these books had been written by two separate people. Alas….these books actually have been written by two separate people, spouses. Which I have no problem with. Except in this case those two separate people don’t seem to have read each other’s contributions.

For sake: 10 book Nordic Noir series….going cheap!!

[kerry cadwallader · Rating 5 out of 5]

I've been waiting for this book to come out in the UK for so long and let me tell you ... IT DID NOT DISAPPOINT ... this has to be the most graphic one yet and I am already sad that we now need to wait whilst this couple write another ... 5 stars always

[Wayne Eklof · Rating 3 out of 5]

2.5*s

[Zachariah Thompson · Rating 2 out of 5]

Honestly was disappointed in this book! Echoed and felt like the first book: “Hypnosis.”
I’d never say I hate a Lars Kepler book, I just expected more risk and excitement in the story line, instead of ghosts from previous books!
Also, need to bring Saga back!
Waiting and excited for the next chapter of the series!

[VP · Rating 4 out of 5]

These books are good page turners.
The ending felt thrown together.

According to one of my previous reviews, I hate Saga. I dont mind her being benched.

Most house doors open inward. This is to prevent being trapped by an outside hazard. they should not have been trapped by a tree falling.

[sav schlosser · Rating 3 out of 5]

Not my favourite Lars Kepler but not the worst. It was just meh

[Victoria Norris-MacLean · Rating 3 out of 5]

I have read all the Joona Linna books so far but this will be my last. The earlier books are much better than this one, I guess I have just moved on to other things.

[Bzz Kolla · Rating 4 out of 5]

Thank you NetGalley and Bonnier Books UK for this eCopy to review

The Sleepwalker is everything I want in a Nordic thriller dark, disturbing, and utterly relentless. From the blood-soaked crime scene in a deserted Stockholm campsite to the psychological depths of trauma and memory, this novel gripped me from the first page and didn’t let go. It’s a story about sleep, secrets, and the terrifying things we’re capable of when we’re not even awake.

🧠 Plot Summary
When police respond to a late-night emergency call at a closed campsite, they find a scene straight out of a nightmare: a man brutally dismembered, blood everywhere, and a teenage boy, Hugo Sand sleeping beside a severed arm. Hugo, the son of a famous author, suffers from a rare form of somnambulism triggered by nightmares. He remembers nothing.

Enter Joona Linna, who enlists hypnotist Erik Maria Bark to unlock Hugo’s memories. But what begins as a search for truth quickly spirals into a hunt for a killer who is not only active but escalating. As Joona digs deeper, he uncovers a chilling pattern and realizes that Hugo may not be the only one sleepwalking through horror.

🔍 What Worked

The Premise: The idea of a sleepwalker possibly committing murder is both horrifying and fascinating. Kepler uses it to full effect, blending science and suspense.
Joona Linna: As always, Joona is a compelling lead—relentless, intuitive, and haunted by his own past.
Pacing: The short chapters and cliff hanger endings make this a compulsive read. I flew through it in two sittings.
Psychological Depth: The exploration of sleep disorders, memory repression, and trauma adds a rich layer to the procedural elements.
Atmosphere: Cold, clinical, and claustrophobic—Kepler’s Sweden is a place where danger lurks in every shadow.

Final Thoughts
The Sleepwalker is a chilling, high-stakes thriller that blends forensic detail with psychological suspense. It’s not for the faint of heart, some scenes are very gruesome and genuinely disturbing, but if you’re a fan of dark crime fiction, this one’s for you.

[Cathy · Rating 4 out of 5]

Big book. Big setting and storyline. And lots of big very creepy scary scenes and murders. Lars Kepler is a remarkable thriller writer (team of husband wife writing duo, the Ahndorils.) who excels at pacing, hooks and page turning aha moments. And characters. So many in this book to keep track of but Joona Linna is the star, a somewhat broken detective who stops at no point to find the killer/s. His team is small but keen, the setting is as much a character as any in this book: Sweden, outside Stockholm, late fall almost the first snowfall of winter, a wild place governed by nature and the elements. The plot: sleepwalker Bruno, a young man of 17, lives with his father Bernard Sands and longtime girlfriend, Agneta, both professionals, he a writer/help columnist, she a journalist. Bruno misses his mom who left him years ago, resents Agneta who's cared for him since he was a small child; Bruno is found at the book's start in a blood drenched caravan, bloody and sleeping on a severed arm surrounded by body parts of a man brutally murdered with an axe. Did Bruno do it? It's confirmed he was sleepwalking. And so this tale begins. There are more murders, similar severed torsos, all men until suddenly there's a woman found dead and dismembered. Bruno checks back in to the sleep clinic where he's undergone observation many times. An old pal of Joona's, Erik Bark, to hypnotize Bruno to find out what he actually saw while sleepwalking. The third time's the charm and many new things come to light, like, the real suspect. More scary, surprising and very creepy events unfold and during a raging blizzard that's more like a tornado of snow.
There should be one of those upfront notes like in tv series: Some scenes may not be for all viewers. Certainly true in The Sleepwalker. Fair warning. No spoilers.