Yes! Another Constant Reader is snapped up. Go Stephen King!
Yes, I'm quite a fan of the guy myself
Misery is a fine choice for the next book to read. Nothing supernatural in
Misery, it's just pure, twisted, human-made horror. It's a very good book.
Lisey's Story is a little unlike his other books; you probably noticed in
The Shining that King does quite a lot of back-tracking, filling in details from the past, and he does this is most of his books (really gives the characters depth, though, and adds to the grittiness that often pervades his novels).
Lisey's Story takes this to the extreme and dwells more on the past than it does on the present day; much more about Lisey's coping in the wake of her husband's death and the reflection on their life together, and the supernatural element is more of a side-link rather than the main focus. But again, although a little different, it's still a very good read, very much full of emotion.
As to the books and the film adaptations of them. Well, it's rare that I see a film adaptation that I prefer more than the book (Lord of the Rings is about the closest it's got to that!) and with King, I definitely prefer the novels. The films themselves are usually quite good in their own right; I enjoyed
The Shining (I don't think anyone can fail to be impressed by Jack Nicholson's portrayal of Jack!),
Dolores Claiborne,
Pet Semetary,
Green Mile etc. But if I have to compare them, I think the book of
The Shining is
so much better (and I'd say the same with all the books, actually). It is about the only book that I've actually found genuinely creepy, and the film misses out the best parts, such as the hedge animals. For that, I cannot forgive Kubrick
And as I read the book before watching the film, I was bemused when the hotel didn't blow up and
very bemused when Halloran was killed! I, myself, liked the sentimentality of the ending in the book, where Jack breaks through his madness, and actually starts injuring himself in order to let Danny escape; it is quite touching and shows how, despite his own turbulent past with his own father, Jack refuses to be the same with Danny; all through the book we see that this is something that really worries Jack, but in the end he is able to fight it.
Blimey, I'm rambling on a bit here! This is what happens when people get me onto Stephen King!
As for suggestions for further reading...ah...how about ever book he ever wrote and will write?
Okay, I think
Misery is a very good start.
Cell is also a good read, a more recent book that is a kind of return to King's good old gory horror. And if you also enjoy fantasy, then you might even be tempted to maybe try
The Dark Tower series one day. Although -- and I usually suggest this -- it's usually wise to read a few of King's other novels before reading
The Dark Tower, in order to get used to his style and also because he alludes to quite a lot of things from his other novels in the Series and it's always interesting when you come across one; it gives deeper levels to the epic story (like the different levels of the tower, if you will
)
Anyway, really, I'm leaving now and I'll stop plying you with all this random information! Hopefully (nay, you
will 
) enjoy whatever book you pick next!