Books similar to "Let The Right One In"?

[Ephemera Pie]

Hi! I'm looking for books that are similar to "Let The Right One In" by John Ajvide Lindqvist. What I'm looking for are books where a MC falls in love with a monster/evil of some kind. Not like Beauty and the Beast, where the beast is actually good, or hot but mean fairies. I'm interested in actual bad monsters, maybe people if I can't find monsters. Any help?