Break My Heart 1, 000 Times - Daniel Waters

Living in the aftermath of the Event means that seeing the dead is now a part of life, but Veronica wishes that the ghosts would just move on. Instead, the ghosts aren't disappearing - they're gaining power. When Veronica and her friend, Kirk, decide to investigate why, they stumble upon a sinister plot. One of Veronica's high school teachers is crippled by the fact that his dead daughter has never returned as a ghost. Veronica seems like the perfect body to host her. And even if he's wrong, what's the harm in creating one more ghost?