City of Bones by Cassandra Clare
It’s after dark in New York City, and Clary Fray is seeing things. The best-looking guy in the nightclub has just stabbed a boy to death – but the victim has vanished into thin air. Her mother has disappeared, and a hideous monster is lurking in her apartment.
With her life spiralling into darkness, Clary realizes that she has stumbled into an invisible war between ancient demonic forces and secretive Shadowhunters – a war in which she has a fateful role to play…