If a book contains ______, you will always read it (and a book or books that contain it)!
Hm. The answer to this used to be “vampires,” but with the current Twilight craze I’ve had to give that up. There’s just too much crap vampire fiction out there. I read a lot of crap stuff back when I first became obsessed with vamps, and eventually figured out how to tell if a book was going to be decent or not pretty quickly and started avoiding the crap ones.
It’s really diminished the number of vampire books I read these days, let me tell you.
I still read quite a number of them, though. The Harry Dresden books have a couple of vampires as recurring characters, and so do a couple of other urban fantasy series I read.