This book by Dima Zales can be found on Amazon. I have to say I am looking forward to the next book.
This book is about a boy who has to do some amazing feats to save himself and his friend Phoe. It's pretty strange at first because the boy (Theo) is in a world where very few adults interact with the kids. There are separate areas surrounded by barriers for children, adults, and the elderly. The children are taught that once they reach a certain physical age they stop aging. When a person dies he or she is simply forgotten by all. It's like the person never existed meaning no one suffers the loss of a friend or loved one, the just simply no longer exist.