Holly Black & Cassandra Clare 
Magisterium: The Bronze Key [EPUB ebook] 

Magic can save you Magic can kill you It should be a time of celebration. The Enemy of Death is dead; a severed head proof of his downfall. The magical world has no reason to believe otherwise, and Callum, Tamara and Aaron are celebrated as heroes.But at a party held in their honour, things go horribly, brutally wrong. A fellow student is callously murdered, and it seems Call s worst fears are confirmed: there is a spy in the Magisterium.No one is safe.Now, using the powerful magic they ve been taught, the trio must risk their lives to track down the killer. But magic is dangerous in the wrong hands it could bring terrible destruction. And reveal the deadliest secret of all . . .