I loved it! I recommended it to my top readers. It can be a little hard to follow, but if you add discussion around it I think it will be OK. It paints a beautiful picture, so it will be great for practicing visualizing.
I highly recommend this book series. I hated Alice in Wonderland as both a kid and adult but this book is much better. I love that there is a different world beneath the Earth's surface and the conflict. Your students will love the adventure and relate to many of the feelings and situations that are explored in the book. I devoured The Hunger Games series and was pleased to find out that Suzanne Collins wrote other books that are just as good!!
Every single kid that I've had read this book has LOVED it! They always devour the series. I tell them to push through because some find the first 1/3 a bit boring, but every single one say that it's well worth the effort.