"Gregor the Overlander" by Suzanne Collins (The Underland Chronicles, Book 1)

This irresistible novel by Suzanne Collins -- international best-selling author of the Hunger Games series --  tells the story of a boy who embarks on a dangerous quest to fulfill his destiny and find his father in a strange world beneath New York City.

When Gregor falls through a grate in the laundry room of his apartment building, he hurtles into the dark Underland, where spiders, rats, and cockroaches coexist uneasily with humans. This world is on the brink of war, and Gregor's arrival is no accident. A prophecy foretells that Gregor has a role to play in the Underland's uncertain future. Gregor wants no part of it -- until he realizes it's the only way to solve the mystery of his father's disappearance. Reluctantly, Gregor embarks on a dangerous adventure that will change both him and the Underland forever.