I have such a spotted history with Stephen King, because I'm afraid I've let many of the stories that are such an ingrained part of our culture pass me by. And that isn't to say I won't catch up with them one of these days, both for better and for worse.
He is such a wonderful writer when he's good. His drawing of characters, and his ability to introduce a place and a situation in the early segments of a book, have never failed to suck me right in. In my view some of them are nothing short of genius. Unfortunately, especially in the latter and really bloated novels, what we're left with is an unfinished masterpiece.
There are so many things I love about certain of his stories that I find it really difficult to make a simple list. Basic highlights would be THE SHINING, THE DEAD ZONE, CHRISTINE, THE LANGOLIERS (people don't often mention that one but it's one of my favorites), the short stories (including '1408'), and THE STAND (oops, I haven't actually read much of that one). Maybe THE DARK HALF, don't remember a lot of it now.
I know I'm leaving out some good ones.
And yes, his non-fiction writing is wonderful.