To those who found the Dark Tower difficult, I'd say try to push past the first book (it's also the one I find the most dull). I think the story really picks up in the second one, and the first half of the third book, The Waste Lands, is some of my favourite stuff that I've ever read.
Depends what you're looking for, really, Gollum! King's written about a variety of things; aliens, ghosts, the undead, zombies, then there's more psychological stuff, very human horror (thinking of that period of Gerald's Game/Dolores Claiborne here). Personally, I think The Shining is the only genuinely creepy book I've ever read...the fire hose and the thing in 217...brr, it raises the goosebumps. He's done some good stuff later on, too (in my opinion); Cell, for its arguable faults towards the end (I don't mind it, but I know others have serious contention with it) gets back to a nice, fact-paced, gory story. Lisey's Story is very emotional, a focus on a couple's relationship, with lots of backtracking and filling in the past, with the supernatural and human horror elements being more of a side story.
To sut myself short, knowing how much I can go on about this guy, I don't reckon you can go much wrong with his earlier stuff. Or, here's a definite suggestion...Insomnia is a definite 'Tower' book, strong connections to it all over the place...seeing as you've read the epic, you could start on Insomnia because there will be some familar ground, but will get you used to King's style in his other work.
