Steven King, at his best, is the greatest American novelist of his generation. His character building is unsurpassed and he can definitely turn a phrase. On the other hand, a lot of his books would have benefited from more aggressive editing and he doesn't always stick his landings. That being said, he's been a fixture in my library for decades.
I'm glad to see others recommend 11/22/63, which IMHO is the best "modern" King novel (and maybe his best ever). For less well known books, I read Duma Key recently and liked it a lot. I know it's been mentioned before, The Talsiman is one of my all-time favorite books.