The Demon's Lexicon by Sarah Rees Brennan

Sixteen-year-old Nick and his older brother, Alan, have have a fierce loyalty to each other. They are on their own, since their father is dead and their mother, who was once a powerful magician, is insane. Now all of the magicians in England are hunting for them with the help of demons, seeking a stolen talisman. The brothers are both quick with weapons and always on the move. Nick has always looked up to Alan, in spite of his soft-hearted ways, but when a young man shows up with his sister, seeking help against demons of their own, Nick begins to suspect that Alan has been lying to him.

Irish author Sarah Brennan has combined suspense, magic, family secrets, brotherly love and twisty action in her first novel. Highly recommended for fans of urban fantasy along the lines of Holly Black's White Cat. Grade 8 - up.