This is a book aimed at middle-schoolers, written by the guy who wrote The Spiderwick Chronicles. I kept seeing this book at my daughter's book fairs, and the artwork and the dustcover blurbs were what interested me.

For adult readers, this may be a bit simplistic in construction, but there's some really good world-building here. By the end of the book, the whole plot seems pretty transparent (for well-read adults, at least), but younger (10-12 year olds) the book has enough sci-fi/fantasy creations to make it a pretty interesting read.