Shawshank and The Body (Stand by Me) are 192 and 128 pages in their paperback releases. I'm sure those are stretched out to fit the publisher's print needs, but they're still pretty decent sized, with plenty of room for the stories to grow and breathe.

Not that your point is invalid, but at least in the case of Shawshank, which is the source material I've read a few times, the movie is all there in the stories. In The Shining and The Green Mile, the movies trimmed material, which I know King isn't usually thrilled about, but was absolutely the right decision.