Audible lists this book as a mystery/suspense thriller, but I definitely got the feeling that it is of the preteen fantasy genre. It is brimming with the standard fears and concerns of most preteen kids whose lives are changing and growing as they do. The fantastical experiences of the main character would actually cause any person or reader to grow mentally from them. I loved the castle of thorns and all of the challenges that it offered! And the imagination involved in the stories and nightmares imagined throughout is beautiful! Beautiful, not as in gorgeous, but as him complex and, well, truly imaginative! Definitely not a waste of time, and, although it's full of great messages and lessons, it's really not preachy!