I'm looking for the name of a book.
I remember reading this book in either 2009 or 2010. It was kind of a futuristic book. they were humans but didn't live on earth.that they lived on this world that someone had invented and it floated around earth. At the beginning the world had three different levels, but as the book, or series i don't really remember, progressed the levels got closer together and the main character went on this journey. he started out working at an orchard on the middle level and didn't get much food or water. he went on a journey to a town on the middle level then climbed up the cliff to the top level. there he met a boy and they did something together, though i don't remember what. later in the book/series he climbed to the bottom level where he met two people and found out there where horrible monsters who would kill you. at the end of the book/series all the different levels became even and the top level flooded and became a big lake where the monsters lived. if you could help me i would greatly appreciate it