City of Bones by Cassandra Clare is the first novel of the Mortal Instruments series, the urban fantasy that opened her enormous Shadowhunter universe. Clary Fray sees a murder in a New York nightclub that nobody else can see, and her ordinary life turns out to have been hiding something very large.
Cassandra Clare’s books have built a passionate readership and many sequels and spinoffs. City of Bones is the natural starting point.