Sunshine and Shadow by mercuralis
This was inspired by Robin McKinley's modern fairy-tale/horror/fantasy "Sunshine." It's sort of Beauty and the Beast--one of the reasons I loved it.
The novel is about an almost average girl, Sunshine, who is kidnapped by vampires. She is chained to the wall of an old abandoned mansion, meant to be dinner and dessert for Constantine, a vampire that they are trying to either break or kill or both. In an odd bit of fate, Constantine spares her life, something vampires never do. In return, when the sun comes up, Sunshine uses her long buried magical ability to allow him to step into the sunlight, thus allowing both of them to escape.