City of Bones

Sixteen-year-old Clary Fray is an ordinary teenager, who likes hanging out in Brooklyn with her friends. But everything changes the night she witnesses a murder, committed by a group of teens armed with medieval weaponry. The murderous group are Shadowhunters, secret warriors dedicated to driving demons out of this dimension and back into their own.
Mortal Intruments 1.

Drawn inexorably into a terrifying world, Clary slowly begins to learn the truth about her family - and the battle for the fate of the world.