A dump site, a key, and a mystery

Lots to think about in Trash by Andy Mulligan. Raphael, Gardo, and Rat are three boys who live in a dump site. Not near, but IN.  All day, they (and hundreds... thousands?) of other kids sort through the endless mountains of trash, trying to find something to sell, trying to survive.  One day they find a leather bag that contains a key, some money, and a wallet.  They decide to keep it, even though the police are offering a reward, and soon they're trying to solve a mystery involving a murder, a strange code, a graveyard, and a corrupt politician.  The story is told in alternating voices of the three boys and occasionally a couple of other characters.  The description of their lives is haunting, because it seems like it could be so real and relentless (being nabbed by the police would be terrifying), and the plot is fast-paced and intriguing.  You'll be thinking of the boys and their situation long after you finish the book.