I haven't read any zombie stories, but I don't get it at all. I'd probably be fine with some alien species behaving that way, but dead humans with salient parts missing that still wander around... aahh, no. But in general, the big kick I get out of science fiction is definitely the way it twists the world and makes you think "wow, things don't have to be like this, if you change x, what would we do?" I'll check them out!