Whisper of Crows by Jameson Hesse

Kanaan James is a disturbed teenage boy obsessed with his childhood friend Abigail Caulfield. A horrible car accident leaves Abigail stricken with amnesia and Kanaan, desperate for her attention, convinces her they are soul mates, running from the law, in the midst of a passionate love affair, while hiding in an old abandoned house deep in the woods, Kanaan is forced to test the boundaries of his own humanity