If you can, track down the audio version of Stephen King reading the first three Dark Tower books. Not only is it the original version of The Gunslinger, but King's voice really brings you into the story. Sadly, starting with book four he fell in love with the voice of a professional reader and only that version is available on CD. King also reads Bag of Bones, another personal story for him.
The final three Dark Tower books suffer because he decided to write them all at once, regardless of what his muse said. With the others, if the story stopped coming to him with the characters in the middle of a Riddle contest, he stopped the book there and waited a half decade before going on. It was the one series that actually felt like it came from somewhere else. Then, after the accident, he forced things so he could guarantee he'd finish them before dying, retiring afterwards. The retirement didn't last long 