Dark Tower is one of my favorite series ever. Also, Marvel did a pretty good job with the comic books.
You might get a bit uh, "confused" as you read the series, book by book, as in "what the hell was King on when he wrote all this" but personally that's what I like about him and the Dark Tower series. In the end, and in a weird way, it all makes sense.
“First comes smiles, then lies. Last is gunfire."
Also, for fans of steam/dieselpunk and Firefly, check out Tales of the Ketty Jay book series by Chris Wooding.