Book 4 was good for backstory, I appreciated it more the second time I read it.
Book 5 was solid. Didn't care much for the preacher's backstory, but I liked the town's story as a whole
Book 6 as stated was borderline unreadable. The Susanah (or however it's spelled) stuff was insanely boring, on top of the King stuff
Book 7...solid mostly, but missed a couple times. I liked the story about the town with the breakers.
Personally I rank the books as 3, 1, 5, 4, 7, 2, 6 (book 2 dragged)
And if he were a little younger I always pictured Dean Winters as Eddie