City of fallen angels - Cassandra Clare

The Mortal War is over, and sixteen-year-old Clary Fray is back home in New York, excited about all the possibilities before her. She's training to become a Shadowhunter and - most importantly of all - she can finally call Jace her boyfriend. But nothing comes without a price. Someone is murdering the Shadowhunters who used to be in Valentine's Circle, provoking tensions between Downworlders and Shadowhunters that could lead to a second, bloody war. And when Jace begins to pull away from her without explaining why, Clary is forced to delve into the heart of a mystery whose solution reveals her worst nightmare: she herself has set in motion a terrible chain of events that could lead to her losing everything she loves. Even Jace.