The Demons Lexicon by Sarah Rees Brennan SIGNED EDITION

Nick and his brother Alan are on the run with their mother, who was once the lover of a powerful magician. When she left him, she stole an important charm - and he will stop at nothing to reclaim it. Now Alan has been marked with the sign of death by the magician's demon, and only Nick can save him.

But to do so he must face those he has fled from all his life - the magicians - and kill them. So the hunted becomes the hunter… but in saving his brother, Nick discovers something that will unravel his whole past…