I like a bit of everything. But am very partial to books about exploration (the Amazon, the Arctic, the seas, Space), medical things (neuroscience and weird scary things), science fiction, and the one that gets the weirdests looks: Regency Romances. But I have to be in a good mood to read those.
Absolutely no Twilight, Barbara Cartland, etc. I think there are standing orders in my family that if I express an interest in anything like that besides wanting to run away screaming, I am to be committed in a very comfy insane asylum.