Name of a book, tiered cake world [duplicate]

Question

I want to know the name of a fantasy book, adventure. The reading is for children/young people. I read it about 10 years ago, I would say that it is a book written in the 2000s, maybe a little earlier. The most notable thing about the book is that its world is shaped like a tiered cake. The higher the level of the cake, the better the living conditions. The protagonist is a boy who works in the worst of levels, in something like a plantation. They used as slingshot weapons. The plot is how the protagonist tries to reach the top by climbing the walls of the circles. I know that at the end of the book he reaches the top, but there he discovered some secret about his world. I know that at least it had a sequel, I don't know if it was two books, a trilogy or more.

Answer 1

After a little more research, I found the book is Atherton: The House of Power by Patrick Carman.

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

....

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 an adventure about the true nature of Atherton, and the crisis threatening to turn his world inside out.