This is the first book in the Underland Chronicles series, and is a captivating read. The characters set off on a quest much like other fantasty stories (such as Lord of the Rings, Rowan of Rin, A Wrinkle in Time, Dragon Rider, Eragon), but this journey depends on the cooperation and trust of an odd collection of creatures who would normally never trust one another. There are traitors, heroes, battles, but no magic. The real scene-stealer in this book is young Boots, who not only turns out to be an important hero in her own right, but whose silly baby talk is just as hilarious as Sunny's in A Series of Unfortunate Events.
Read this book if you love adventure, hero tales, fantasy, quests, of if you've ever wondered what may happen if you fell into a sewer and kept going. It's not an easy book (similar in difficulty to Dragon Rider), but is much easier than Eragon.