Alcatraz - Brandon Sanderson

On his thirteenth birthday, Alcatraz - a foster child - gets a bag of sand in the mail which purports to be his 'inheritance' sent from his father and mother. The Librarians, of course, immediately steal the bag of sand from him.

This sparks a chain of events which leads Alcatraz to realize that his family is part of a group of freedom fighters who resist the Evil Librarians - the secret cult who actually rule the world. Alcatraz's grandfather shows up and tows him off to infiltrate the downtown library to steal back the mystical bag of sand. The ensuing story involves talking dinosaurs, sentient romance novels, and a dungeon-like labyrinth hiding beneath the innocent-looking downtown library.