Wholesale Demon's Lexicon by Sarah Rees Brennan

[Margaret K. McElderry Books] When his brother’s life is put in danger, a teen whose family has been on the run as long as he can remember must infiltrate London’s magical underworld in this gripping first book in the Demon’s Lexicon urban fantasy trilogy. Nick has spent his life fleeing from magicians with his older brother Alan, haunted by a mother who recoils from his touch and the memory of a murdered father. When Alan is branded with a deadly demon mark, the only hope for survival is to kill a magician—a task that plunges them into a deadly game of cat and mouse through the city’s supernatural underworld. As Nick and Alan navigate the treacherous world of the Goblin Market and confront the sinister Obsidian Circle, Nick begins to suspect his brother has been hiding the truth about their past. Loyalties are tested and betrayal looms, forcing Nick to choose between protecting the only family he has left and facing the possibility that everything he’s believed is a lie.