I always get into my King mood during spring.
All of his books are mature- with language, violence, and sexual themes...but they are very interesting and always a page turner. The imagery is wonderful. He's one of those authors who creates a separate world for you. After reading his novels, I confuse myself. I always seem to think I saw a movie about the novel. The imagery is just that great. He mainly deals with science fiction. I can't think of a non-sci-fi book of his, actually. Of course, everyone is familiar with "The Shining." My first King read was "Desperation." If you can take the heat, go with the King. The made for T.V. specials and movies adaptations are definately not as good as the novels, so don't get a false impression.
I enjoy King's books, too. He's actually one of the best short story writers out there, I think. I recommend picking up one of his short story collections.
I haven't read Stephen King since "The Tommyknockers" scared the sh** out of me when I read it too young. I'd recommend his book "On Writing" though, if you're interested in the craft.