The Demon's Lexicon by Sarah Rees Brennan - Nick has been on the run for as long as he can remember. His mother stole a charm off of a very powerful magician before he was born, and he wants it back. He and his older brother, Alan, move around the country with their deranged mother to escape the magicians and the demons the magicians send after them. But then Alan gets a demon mark - a mark that leads to possession and then death - when he tries to help two other teenagers who are in trouble. Nick is the only person who can save him, but that gets harder to do when he starts to think Alan is hiding things from him.
