Gegen Das Schicksal by Veronica Roth

Years after a small band of teenagers thought they had saved the world by killing a supernatural enemy, the surviving heroes struggle with fame, guilt, addiction and fractured lives as they try to build ordinary futures; when a new string of brutal events tied to their past begins to surface, the narrator is forced back into a dangerous investigation that forces the group to confront the long-term cost of their victory, the ways trauma reshapes identity and relationships, and whether destiny can be escaped or must be fought again.