I wrote my first book in the 1st grade. All right, I dictated my first book in 1st grade. I hadn't learned how to use a typewriter yet. The book was about aliens in the grocery store.
My genre of choice has not changed much. The most important thing about a story is the story. I just find a story is more interesting if you throw in a zombie, fairy, demon, or something unexpected that the characters have to deal with.