From
StephenKing.com:
Stephen's Rewritten the Gunslinger
To bring the language up to date, and the style in line with the style of the other Dark Tower volumes, Stephen's rewritten The Gunslinger. The new version, available in June 2003, will also be released in audiobook format.
It's probably available already. I think I'll check it out myself, it's a pretty thin book and (in its original form) it's my favorite book of the series. Dark Tower 5 is set for November, right now, and then two more books will follow to conclude the series.
The Dark Tower series are kind of a weird mixture of fantasy, westerns, sci-fi and regular King. The main character is sort of a cowboy/knight from another world that is both post-apocalyptic and like human Middle Ages, but he later gets help from people from various time periods of "our" world.