Oh, oh, if I may add something, then...(I say this to everyone who starts the
Dark Tower series!) If you find
The Gunslinger a little slow paced, or generally not to your liking, I
command (heh) you to push on to the next book,
The Drawing of the Three. I don't really like
The Gunslinger, personally, but after that the series is fantastic (especially the third book!) Mind you, you might (hopefully!) really enjoy it!
As for the other Stephen King books...well, you really can't go wrong with any King books in my opinion! And also, if you read more of his other novels, like
The Stand,
'Salem's Lot, etc, there are a few things in
The Dark Tower series that you'll understand to a greater extent.
The Dark Tower is like the axis around which all of King's books rotate, which references to quite a few. They're not so large that you wouldn't understand the series without reading the other books, but it certainly allows you to pick up on the little nuances.
And also just read other King novels because the guy writes some real ripping yarns. I guess his style isn't to everyone's liking, but there's no denying that he can tell a good story!
Hitchhiker's Guide to the Galaxy is an excellent book as well! A fantastic comedy sci-fi. Douglas Adams was such a legend