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Emily Windsnap #10
Emily Windsnap and the Crystal Caves
Join the entire gang of mer-friends—and celebrate twenty years of Emily Windsnap—in this epic and masterfully crafted adventure by New York Times best-selling author Liz Kessler.
Adventure always seems to find Emily Windsnap! So when she discovers a bangle with a unique crystal under Rainbow Rocks, she and her friends are soon unraveling a whole new mystery. After learning that the crystal originally came from a familiar place—Halflight Castle!—Shona and Emily reunite there with Aaron . . . and none other than Neptune, king of the oceans. The bangle leads the mermaids to a cave full of crystals, and, with Mandy's help, they discover the truth about the jewel’s origin—and what’s at stake if they don’t make things right. Unfortunately, the only solution involves getting the sea and sky’s most powerful (and notoriously selfish) rulers to put their own interests aside for the greater good. Will the quartet find a way to convince the imperious Neptune and the Viking god Thor to come together to prevent disaster?
Adventure always seems to find Emily Windsnap! So when she discovers a bangle with a unique crystal under Rainbow Rocks, she and her friends are soon unraveling a whole new mystery. After learning that the crystal originally came from a familiar place—Halflight Castle!—Shona and Emily reunite there with Aaron . . . and none other than Neptune, king of the oceans. The bangle leads the mermaids to a cave full of crystals, and, with Mandy's help, they discover the truth about the jewel’s origin—and what’s at stake if they don’t make things right. Unfortunately, the only solution involves getting the sea and sky’s most powerful (and notoriously selfish) rulers to put their own interests aside for the greater good. Will the quartet find a way to convince the imperious Neptune and the Viking god Thor to come together to prevent disaster?
240 pages, Hardcover
Published May 6, 2025
About the author
Liz Kessler
46 books985 followersLiz Kessler is the author of three novels about Philippa Fisher as well as the NEW YORK TIMES best-selling Emily Windsnap series. She lives in Manchester, England.
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Displaying 1 - 23 of 23 reviews
June 7, 2025
I’ve been a huge fan of the Emily Windsnap books since I was a kid! I was so excited when I saw a new book was coming out and even though I’m an adult now I couldn’t wait to read it. Well the book did not disappoint. I enjoyed every second I was reading it and could not put it down! I finished it within 24 hours and was sad to be done so soon. I really liked the educational component of this book like fault lines and tectonic plates. I remember being in high school and learning about those things so it was nice to see Emily connecting them to her real life. I love seeing her grow into her own person as each book progresses and I can’t wait to see what she does next!
May 8, 2025
Thank you, NetGalley and House of Zeus for the early copy of this book.
I think this is a really great adventure fantasy fast pace for a younger audience in the fantasy genre. It was a quick read enjoyable had some really interesting history and science mixed in. I think for young fantasy readers this would be a really great book to read.
I think this is a really great adventure fantasy fast pace for a younger audience in the fantasy genre. It was a quick read enjoyable had some really interesting history and science mixed in. I think for young fantasy readers this would be a really great book to read.
July 14, 2025
Such a throw back and very, very cute and summery!
August 5, 2026
When I saw that there was a new addition to one of my favorite childhood series, I knew I had to read it! But unfortunately, I was pretty disappointed. The plot was just not very interesting and I didn’t like the writing very much.
January 7, 2025
*free copy from NetGalley in exchange for an honest review*
As a teenager, I read some of the original Emily Windsnap books (most memorable being Castle in the Mist, I adored that book), so having the chance to read an ARC of Valley of the Vikings filled me with absolute joy. It's been a few years, so I remembered the main cast - Emily, Shona, Aaron. Not sure if I remember Mandy or if she was in a later book, it's been over a decade!
As I understand it, this is a capstone to the original series, featuring a more mature Emily than I remember, in her endeavours to save the world from an underwater volcano that would essentially wipe out civilisation as we know it. Her main antagonist is, once again, King Neptune, and I very much enjoyed seeing Emily's view of him change from one of fear to one of disgust. There's an underlying current (ha) to this book of growing up and learning to think critically of authority figures, which is important to the youth of today. There is also a very strong anti-war message to this novel, which I whole-heartedly appreciate. It is shown very clearly as something caused by the greed of men who think that they are more powerful than they actually are, and the sheer devastation it causes to people. Emily's entire speech towards the end of the book gave me absolute chills.
In terms of the characters, I feel like you'd have to have read the original series to know what they're like because in this novel they felt a little...flat? Of the four child protagonists, they all speak the same way and I noticed that there is very little in the way of physicality to SHOW their character. In fact, of all the characters in the book, the most interesting were Mr Beeston and Millie - everyone else just struck me as very bland this time around. Actually, Rolf was a strong contender for my favourite side character in this book - he had a very different take on optimism to the others, and I appreciated the different ways in which the group of characters he is involved in were reacting to the story.
It's been a hot while since I read the earlier books, and it was interesting to me that Emily and Aaron had broken up but remained friends. I really liked this, as it showed a maturity to them both as people, however this was undermined by the odd comment from Emily that drew attention to it, particularly one moment at the end about them holding hands. I do, on the one hand, understand why it would cross her mind and to be fair, it really is only mentioned once or twice. On the other, I don't know why it needed bring up again at the very end of the book?
Speaking of characters, let's talk about THOR. The fact that he and Neptune are from completely different mythologies is not addressed even once, which I find hilarious and actually kind of love. I also loved the little cameo of Loki and actually had to put the book down for a moment because I got so excited seeing their name. I obviously understand why Thor is only in the last third or so of the book, however it might have been nice to see him earlier on, if only in a flashback.
This was a quick read, relatively simple to follow, and a nice end point for anyone who was a fan of the Emily Windsnap books as a child/teenager, or for any child currently reading them!
Tl;dr: Quick read, strong messages, characters felt a little flat for most of the book, would still recommend for fans new and old. 4 stars.
As a teenager, I read some of the original Emily Windsnap books (most memorable being Castle in the Mist, I adored that book), so having the chance to read an ARC of Valley of the Vikings filled me with absolute joy. It's been a few years, so I remembered the main cast - Emily, Shona, Aaron. Not sure if I remember Mandy or if she was in a later book, it's been over a decade!
As I understand it, this is a capstone to the original series, featuring a more mature Emily than I remember, in her endeavours to save the world from an underwater volcano that would essentially wipe out civilisation as we know it. Her main antagonist is, once again, King Neptune, and I very much enjoyed seeing Emily's view of him change from one of fear to one of disgust. There's an underlying current (ha) to this book of growing up and learning to think critically of authority figures, which is important to the youth of today. There is also a very strong anti-war message to this novel, which I whole-heartedly appreciate. It is shown very clearly as something caused by the greed of men who think that they are more powerful than they actually are, and the sheer devastation it causes to people. Emily's entire speech towards the end of the book gave me absolute chills.
In terms of the characters, I feel like you'd have to have read the original series to know what they're like because in this novel they felt a little...flat? Of the four child protagonists, they all speak the same way and I noticed that there is very little in the way of physicality to SHOW their character. In fact, of all the characters in the book, the most interesting were Mr Beeston and Millie - everyone else just struck me as very bland this time around. Actually, Rolf was a strong contender for my favourite side character in this book - he had a very different take on optimism to the others, and I appreciated the different ways in which the group of characters he is involved in were reacting to the story.
It's been a hot while since I read the earlier books, and it was interesting to me that Emily and Aaron had broken up but remained friends. I really liked this, as it showed a maturity to them both as people, however this was undermined by the odd comment from Emily that drew attention to it, particularly one moment at the end about them holding hands. I do, on the one hand, understand why it would cross her mind and to be fair, it really is only mentioned once or twice. On the other, I don't know why it needed bring up again at the very end of the book?
Speaking of characters, let's talk about THOR. The fact that he and Neptune are from completely different mythologies is not addressed even once, which I find hilarious and actually kind of love. I also loved the little cameo of Loki and actually had to put the book down for a moment because I got so excited seeing their name. I obviously understand why Thor is only in the last third or so of the book, however it might have been nice to see him earlier on, if only in a flashback.
This was a quick read, relatively simple to follow, and a nice end point for anyone who was a fan of the Emily Windsnap books as a child/teenager, or for any child currently reading them!
Tl;dr: Quick read, strong messages, characters felt a little flat for most of the book, would still recommend for fans new and old. 4 stars.
August 8, 2025
This is a truly superb fantasy adventure for children with an honest but empowering message for us as individuals and for our planet.
Blending mermaids, magic, Vikings and norse mythology in a wonderful and gripping tapestry of narrative with genuine characters who pull you along from once chapter to the next.
There is a strong environmental theme, regarding not the sea specifically but the harm that is done to our planet and the consequences if we, as a people of the planet, allow it to be abused by those seeking wealth at any cost. Those who admire Greta Thunberg would appreciate this story.
As a fan of mythology and Vikings I felt that Liz represented them very well. Yes there are Horned helmets, but that's how a common visual clue for a character being a Viking. What really impressed me was that Liz showcases the Vikings as traders, crafts people, and also positioned a woman as the leader of one particular group. These are angles to Viking culture and society I feel should be promoted more. So I salute Liz for her clever creative choices in this regard.
I genuinely look forward to the day I can share this with my daughter when she is old enough to understand and enjoy and learn from this delightful mixing of Myths and magic. With a nice dollop of environmental science thrown in during the century of climate crisis.
Blending mermaids, magic, Vikings and norse mythology in a wonderful and gripping tapestry of narrative with genuine characters who pull you along from once chapter to the next.
There is a strong environmental theme, regarding not the sea specifically but the harm that is done to our planet and the consequences if we, as a people of the planet, allow it to be abused by those seeking wealth at any cost. Those who admire Greta Thunberg would appreciate this story.
As a fan of mythology and Vikings I felt that Liz represented them very well. Yes there are Horned helmets, but that's how a common visual clue for a character being a Viking. What really impressed me was that Liz showcases the Vikings as traders, crafts people, and also positioned a woman as the leader of one particular group. These are angles to Viking culture and society I feel should be promoted more. So I salute Liz for her clever creative choices in this regard.
I genuinely look forward to the day I can share this with my daughter when she is old enough to understand and enjoy and learn from this delightful mixing of Myths and magic. With a nice dollop of environmental science thrown in during the century of climate crisis.
April 26, 2025
Valley of the Vikings by Liz Kessler is the tenth story featuring half human, half mermaid Emily Windsnap and is a great middle grade story that blends adventure, humor, and heartfelt friendships. Emily and her friends discover a hidden island with a whole ship full of 1000 year old Vikings living on it and there is a very imminent danger to the safety of the world, which can only be sorted if the children manage to reconcile Neptune and Thor.
Kessler creates vivid, likable characters that young readers can easily root for, and she balances the action with moments of reflection and personal growth. There’s a definite ecological theme and insightful musings on what it means to be a leader and there’s also a gentle message about courage, teamwork, and understanding different cultures.
The pacing is quick without feeling rushed, making it a great pick for readers aged 7–11 who enjoy action-packed yet heartfelt stories. Kessler’s writing is accessible but never talks down to her audience, and there’s a nice sprinkle of humor throughout that keeps the tone light even when the stakes get high.
Kessler creates vivid, likable characters that young readers can easily root for, and she balances the action with moments of reflection and personal growth. There’s a definite ecological theme and insightful musings on what it means to be a leader and there’s also a gentle message about courage, teamwork, and understanding different cultures.
The pacing is quick without feeling rushed, making it a great pick for readers aged 7–11 who enjoy action-packed yet heartfelt stories. Kessler’s writing is accessible but never talks down to her audience, and there’s a nice sprinkle of humor throughout that keeps the tone light even when the stakes get high.
December 21, 2025
A fun addition to this series - it’s a classic Emily Windsnap-type plot, but because it follow that pattern it feels like a rehash of previous plots in a new skin
(also not me hoping Archie will make an appearance even after eleven years of NOTHING)
(also not me hoping Archie will make an appearance even after eleven years of NOTHING)
June 19, 2025
What worked:
Humans and merfolk live together, and Emily is the daughter of a merman father and a human mother. The author resolves the logistics of living together by making their home on a boat. Emily has a human best friend named Mandy, and they attend high school together. Her mermaid best friend is Shona, and they attend Shiprock School with other merkids. She has remained friends with Aaron, an ex-boyfriend, and he joins Emily and Shona on their adventure to the ocean floor. The story is told in Emily’s first-person point of view.
Early on, the plot moves at a quick pace, which will appeal to young readers. Emily finds the bangle in chapter one and is already traveling to Halflight Castle by chapter three. The kids discover several improbable characters later, and the story slows down. However, these characters provide valuable information about past events, adding urgency and suspense. The plot’s tempo picks up again as Emily and her friends try to stop an impending disaster that can only be resolved through the cooperation of Neptune and Thor. How do they change the minds of two greedy gods?
The author may be sharing an opinion about environmental issues caused by humans. The crystal on Emily’s bangle comes from lava after a volcanic eruption in the ocean. Neptune orders his merfolk to mine the crystals as fast as they can, but his greed gets out of control. He always wants more wealth and extravagance, which also applies to the Norse god Thor. The prologue describes the war waged between these two gods and the far-reaching effects of their insatiable need to possess more. The crystals have a way to rebel against the abuse, but there may be a way to appease the Earth. The crystals seem to have a mind or spirit that reacts to the actions of humans and the gods.
What didn’t work as well:
The problem with a quick-moving plot is that it doesn’t go into great detail or description. Characters aren’t fully developed, although readers can learn more about them by reading the whole series.
The final verdict:
This book is the tenth in the series, but readers can still enjoy it independently. They’ll like the teamwork shown by the four friends, which is necessary to force cooperation on two greedy, stubborn gods. I recommend you give this book and the series a shot.
Humans and merfolk live together, and Emily is the daughter of a merman father and a human mother. The author resolves the logistics of living together by making their home on a boat. Emily has a human best friend named Mandy, and they attend high school together. Her mermaid best friend is Shona, and they attend Shiprock School with other merkids. She has remained friends with Aaron, an ex-boyfriend, and he joins Emily and Shona on their adventure to the ocean floor. The story is told in Emily’s first-person point of view.
Early on, the plot moves at a quick pace, which will appeal to young readers. Emily finds the bangle in chapter one and is already traveling to Halflight Castle by chapter three. The kids discover several improbable characters later, and the story slows down. However, these characters provide valuable information about past events, adding urgency and suspense. The plot’s tempo picks up again as Emily and her friends try to stop an impending disaster that can only be resolved through the cooperation of Neptune and Thor. How do they change the minds of two greedy gods?
The author may be sharing an opinion about environmental issues caused by humans. The crystal on Emily’s bangle comes from lava after a volcanic eruption in the ocean. Neptune orders his merfolk to mine the crystals as fast as they can, but his greed gets out of control. He always wants more wealth and extravagance, which also applies to the Norse god Thor. The prologue describes the war waged between these two gods and the far-reaching effects of their insatiable need to possess more. The crystals have a way to rebel against the abuse, but there may be a way to appease the Earth. The crystals seem to have a mind or spirit that reacts to the actions of humans and the gods.
What didn’t work as well:
The problem with a quick-moving plot is that it doesn’t go into great detail or description. Characters aren’t fully developed, although readers can learn more about them by reading the whole series.
The final verdict:
This book is the tenth in the series, but readers can still enjoy it independently. They’ll like the teamwork shown by the four friends, which is necessary to force cooperation on two greedy, stubborn gods. I recommend you give this book and the series a shot.
June 29, 2025
In what Liz Kessler calls one last Emily Windsnap adventure teenage Emily enlists her friends from the human and mer worlds to get rival deities Neptune and Thor to rekindle their former friendship to save the planet from disaster.
The popular children’s series begins with preteen Emily Windsnap discovering when she jumps into the pool for swimming lessons that her legs fuse into a mermaid tail and reform as human legs when she gets out. In subsequent adventures, while tackling planetary threats like krakens and pirates, Emily discovers a family secret, that her father is full mer and was imprisoned by Nepture for marrying Emily’s mother, a human, gets her father released from prison to become Neptune’s trusted advisor, convinces humans and mer to put aside their longstanding mistrust and work together, learns to balance the social challenges of being half-human and half-mer, and navigates the emotional impacts of having a boyfriend.
Though not as creative as some of the other books in the series, in Emily Windsnap and the Crystal Caves, teenage Emily learns that she has a voice, stands up to adults for what is right, and faces her fears with poise and strength.
Note: After the success of the Emily Windsnap series recently Liz Kessler has turned her attention to other genres. When the World Was Ours is a provocative story of three children whose lives and friendship is changed as a result of the holocaust during World War II. Entirely different from Emily Windsnap, When the World Was Ours shows the breadth of the author’s writing ability and I highly recommend it.
The popular children’s series begins with preteen Emily Windsnap discovering when she jumps into the pool for swimming lessons that her legs fuse into a mermaid tail and reform as human legs when she gets out. In subsequent adventures, while tackling planetary threats like krakens and pirates, Emily discovers a family secret, that her father is full mer and was imprisoned by Nepture for marrying Emily’s mother, a human, gets her father released from prison to become Neptune’s trusted advisor, convinces humans and mer to put aside their longstanding mistrust and work together, learns to balance the social challenges of being half-human and half-mer, and navigates the emotional impacts of having a boyfriend.
Though not as creative as some of the other books in the series, in Emily Windsnap and the Crystal Caves, teenage Emily learns that she has a voice, stands up to adults for what is right, and faces her fears with poise and strength.
Note: After the success of the Emily Windsnap series recently Liz Kessler has turned her attention to other genres. When the World Was Ours is a provocative story of three children whose lives and friendship is changed as a result of the holocaust during World War II. Entirely different from Emily Windsnap, When the World Was Ours shows the breadth of the author’s writing ability and I highly recommend it.
May 16, 2026
After the birth of my daughter, I've been looking for reading gems to equip her throughout her childhood. And that's how I discovered the Emily Windsnap book series by Liz Kessler.
It's about a girl who is half mermaid, half human and always on the hunt for adventure, always with the support of her family and friends.
The tenth book in the series has just been released. "Emily G and the Crystal Caves" is another crazy adventure for Emily.
A delightful read for young and old, I loved it ❤️
It's about a girl who is half mermaid, half human and always on the hunt for adventure, always with the support of her family and friends.
The tenth book in the series has just been released. "Emily G and the Crystal Caves" is another crazy adventure for Emily.
A delightful read for young and old, I loved it ❤️
September 15, 2025
I love that everybody's character grew so much throughout the series; Beeston finally grew a backbone, Emily truly read Neptune to filth, and she's more likable overall as a person. The vast majority of the book was pretty epic, but I wish at the very end we could have seen how the adults process these insane events Beeston, the Windsnap parents etc. That part felt too abrupt for me. Like, your kid overthrows a god-king, but you don't discuss the aftermath, bruh.
P.S. The cover is stunning!
P.S. The cover is stunning!
December 22, 2025
The last Emily Windsnap book! It took us all year, but we did it! We read the whole series. My sister is pretty disappointed we don't have any more to read. Now we have to find something new to pick up. This book was a lot of fun to read. We had a good time with it and had a good time with the series as a whole. Kind of amazing that the year we decided to read the series together was the year she came out with one last book. It was fate <3 lol.
July 8, 2025
a good end to the series
July 23, 2025
Another great adventure that Emily embarks on! This one is fast paced and full of suprises. The ending is great too.
August 14, 2025
I can't wait for book 11!! I hope it comes out soon
April 12, 2026
This book was so fun to read!🩵
June 22, 2026
I loved the plot of this book. I enjoyed the addition of Vikings and Thor to the mermaid world. The end of the book was a great finish to the series.
June 26, 2026
Been WAITING since book one for Millie and Neptune to finally flirt 🙌🙌🙌🙌
This entire review has been hidden because of spoilers.
August 21, 2026
Neptune (Roman god) has been an established character since book one. There is an entire pantheon of Roman gods to pull from and she chose to introduce Thor and Loki……
August 20, 2026
I’m going to miss re reading this series :/
June 28, 2025
Our narrator Emily is a half-mermaid, half-human girl, which is very much a rarity. When she and a friend stumble on a bejewelled bangle deep in the sea they find out the gem is a very scarce thing, from a very rarefied and magical place. Once there they see news that suggests a missing hoard of such treasures (courtesy a boat sinking that we saw about in the prologue) – but none of her friends will ever expect what is to come about as they seek the wreck and the rest of the mystery...
This comes about as a bit of an outlier – the ten (count 'em!) books already this series would, I guess, have seemed complete. And to a newcomer it's easy to see what bits here are purely on these pages to catch us up to speed for the start of further books, with friendships changed and job promotions made – but it's also easy to see that there is nothing to explain the characters' ability to speak underwater, or how Emily can change just her tail to adapt to be a mermaid – but still manage to breathe underwater. Or how clothing works when you make said transition and are a bloke, like her ex-boyfriend Aaron.
Obviously these details could have been covered ad nauseam before – and I dare say these books are fine; it's just this is not perfect as a jumping-on point. For one thing, this came out as really quite wordy – people discussing this, that and the other and the action being left to one side almost. And what they're discussing is a thinly-disguised environmental message, that proves to be really quite heavy on the unsubtlety. Which kind of makes all the negotiating a bit annoying when you want more fanciful drama, and more so when a key conversation has to leave one of the main characters of it out entirely, for no reason, as if he was never there.
Also this seemed to me to be written in a slightly old-fashioned style, not quite on trend with the latest MG novels. "Swishy", it isn't. But it's not something I could dismiss. For fans who never expected this to come out this must be manna from heaven – their notable characters returning to fit into yet another fantasy action piece. And some of the writing is certainly of a four-star standard. It's just I found some decisions and sections that weren't – they were much closer to a three – and so this gets the obvious halfway house of three and a half.
This comes about as a bit of an outlier – the ten (count 'em!) books already this series would, I guess, have seemed complete. And to a newcomer it's easy to see what bits here are purely on these pages to catch us up to speed for the start of further books, with friendships changed and job promotions made – but it's also easy to see that there is nothing to explain the characters' ability to speak underwater, or how Emily can change just her tail to adapt to be a mermaid – but still manage to breathe underwater. Or how clothing works when you make said transition and are a bloke, like her ex-boyfriend Aaron.
Obviously these details could have been covered ad nauseam before – and I dare say these books are fine; it's just this is not perfect as a jumping-on point. For one thing, this came out as really quite wordy – people discussing this, that and the other and the action being left to one side almost. And what they're discussing is a thinly-disguised environmental message, that proves to be really quite heavy on the unsubtlety. Which kind of makes all the negotiating a bit annoying when you want more fanciful drama, and more so when a key conversation has to leave one of the main characters of it out entirely, for no reason, as if he was never there.
Also this seemed to me to be written in a slightly old-fashioned style, not quite on trend with the latest MG novels. "Swishy", it isn't. But it's not something I could dismiss. For fans who never expected this to come out this must be manna from heaven – their notable characters returning to fit into yet another fantasy action piece. And some of the writing is certainly of a four-star standard. It's just I found some decisions and sections that weren't – they were much closer to a three – and so this gets the obvious halfway house of three and a half.
December 28, 2025
Valley of the Vikings sees the triumphant return of Liz Kessler's beloved half-mermaid, Emily Windsnap, in a standalone adventure that masterfully blends Norse mythology with underwater magic. When a clash between Neptune and Thor sinks a Viking longship and scatters powerful blue crystals, it sets off a chain of events that Emily and her friends must unravel a thousand years later to prevent disaster.
Kessler is a master of high-stakes, feel-good fantasy. This story delivers everything fans love: a breathless treasure-hunt pace, the warm dynamics of Emily’s human and mer team, and a clever plot that hinges on diplomacy and bravery over brute force. The expansion of the Emily Windsnap universe into Viking lore feels fresh and exciting, offering a perfect gateway for new readers while delivering the magical comfort longtime fans expect.
Kessler is a master of high-stakes, feel-good fantasy. This story delivers everything fans love: a breathless treasure-hunt pace, the warm dynamics of Emily’s human and mer team, and a clever plot that hinges on diplomacy and bravery over brute force. The expansion of the Emily Windsnap universe into Viking lore feels fresh and exciting, offering a perfect gateway for new readers while delivering the magical comfort longtime fans expect.
Displaying 1 - 23 of 23 reviews