King's "Misery" with out a doubt the only book I can remember giving me nightmares.
The scene where Annie cuts off Paul's foot for going out screwed me up for days. That scene in the movie was almost laughable compared to what King originally wrote.
I read the book right after it came out and at the time I worked with a woman who looked a lot like Cathy Bates, especially as she looked in the movie. I had nightmares of her cutting off my foot and that was long before the movie came out, Mr. King if you are reading this, you are a great writer, but you really are a sick puppy!
Thats the best part of King's books, he pulls you into the story and makes you live it, and honestly I don't like his writing style.