As I recall, the book was a recent novel that was about a boy on a planet (maybe the Moon? somewhere near to Earth) with three tiers. The top tier was for the rich inhabitants, the middle tier was where ordinary people lived, and the bottom tier was mysterious. The boy tries to climb his way to the top tier but is imprisoned in the bottom tier where there are all kinds of terrifying monsters like big weird centipedes. I think the book was the first in a series of three.
Oh nevermind I found the book. It's Atherton: The House of Power.
Atherton's society is closely knit to its physical geography. Unlike other planets, Atherton is not shaped like a sphere. Rather, it is shaped roughly like an elongated birthday cake, with each layer having less circumference than the one below it. Atherton has three layers: the Flatlands, the bottom and most barren layer; Tabletop, the middle and most widely-populated layer; and the Highlands, the highest layer where governmental figures reside in the House of Power.
Edgar – An orphaned Tabletop-dweller who works in the Grove. He enjoys climbing the hazardous cliffs that form the edge of the Highlands layer. While climbing, he finds a book that plunges him into adventure about the true nature of Atherton, and the crisis threatening to turn his world inside out.