I read the first book some years ago and didn't like how he released it with the original text, unedited. I understand why King didn't want to alter the original writing, but I found that first part such a clumsy read that it completely removed me from the drama of the later, better written portion of the book.
As i understand it, King also published a revision of the first book where he cleaned up the verbiage so it reads better. I should give it a try.
My wife has read the entire series, including all the spinoffs, and is sort of a geek on the Dark Tower. It's probably her second favorite series (after Potter.) She knows about all the other King stories that are supposedly tied to the mythology (such as The Mist) and is a huge fan of it. She keeps encouraging me to read it. Maybe I'll snag me some mobis and go to town.
But after I finish up Brent Weeks' Night Angel trilogy first. That is a really great, fun series to read.