I think that most readers will either love or hate this book and that there won't be very little in between. This story is a story about a story and it's sharing and passing along. The people involved in the discussion are warm and interesting and their personalities are exposed through their interaction. I like them.
The story they tell is the catalyst to understanding them, a passing of the torch so to say. If you view the book from this perspective it's a very satisfying read. If you get immersed in the story that's being told, you may be very frustrated because it doesn't come to a satisfying conclusion and leaves a lot of points un-answered or un-resolved.
The one thing I didn't like was Stephen King's afterward, much like I didn't like what he had to say at the end of the Dark Tower series. It's not that what he says is bad by any means, I just don't believe that he needs to explain himself. It almost ventures into becoming an apology. There's no need to do that, this book (and the Black Tower series) speaks for itself. I feel that including his final perspective or "rationalization" in some way demeans or belittles each story by treating the readers as if they won't understand what he was trying to do without having it pointed out to them. I say let the work stand on it's own, because they do. Let us take it as we will!
And, I like this book!