The Road to The Dark Tower - Exploring Stephen King's Magnum Opus, by Bev Vincent. Bought it at Borders a couple of weeks ago - finished reading it sitting on the deck with a cup of coffee this morning! It was great! Like a trip down memory lane with insight and info added! I highly recommend adding this book to anyone's collection!
(Judging by the number of exclamation points in what I just wrote, it's possbile that I may have had too much coffee this morning)
Completely agree (not about the coffee though!), a MUST for any DT fan IMO.