I'm a little dismayed to see other reviewers calling this book 'cute' and 'fun.' That is misleading. This is a stunningly beautiful book, with evocative imagery and an inspiring message. But it's dark. It is about a girl who sets out on a quest to rescue her twin brother who is trapped inside his nightmares. The book deals with depression and anxiety; the nightmare is a metaphor for the darkness this child is trapped inside.
It's a powerful book, worthy of your time, and it's an appropriate read for a child who is struggling with a mental health diagnosis, or one who is opposed to seeking medical care in order to get that diagnosis or treatment. But it's not a light, fluffy read.
Now, it's also not all darkness. There is lightheartedness and whimsy as well. Talking animals, typical goofy kids, wise-cracking teachers. But to say that the book is cute is a real misstatement, especially if it results in readers picking up this book looking for a fun, quirky read.
***TRIGGER WARNINGS: Features a wheel-chair bound character and one who has limited function due to a stroke, both children. And a warning, when the disabled children enter the dream world, they are no longer physically disabled. Readers may want to know that going in. I'm uncertain how a reader with a physical disability will feel about that depiction. Also features a parent deployed to a war zone, and lacks finality at the end of the book about that person's well-being after a blackout occurs, which might be triggering for children in the same circumstance. ***
The ending is hopeful and satisfying, but not saccharine or unrealistic. Some threads remain unresolved, just like real life.
I highly recommend, but I encourage you to go in with a realistic expectation for what this book has to offer.