Young Adult Literature, Adventure
Chomp is young adult literature because the main character, Wahoo, is a teenager. The book is mainly from his perspective, and in this way the book is oriented toward older children and teens. Not that your mom won't love this book too, because she totally could.
Remember when there was a whole lot of excitement churning on the tree island? A drunk guy with a gun, Mickey pushing his luck, Link fading quickly, Wahoo finding Derek who is totally delirious with an exotic infection and hallucinating? All of that action and tension came from the fact that this story is an adventure… or this story is an adventure because of all of that action and tension. (It's kind of like the age-old chicken and egg dilemma… which do you think came first?) The characters leave home, have brand new experiences, and there is an element of danger around every corner.