I tried to read the book and it sucked. They did him a favour really.
Personally, I think King's stories just don't translate very well to movies, unless (as with Kubrick's "The Shining") huge liberties are taken with the source material. Most adaptations I've seen of his stories were just bad.
Eh it comes off as a corny and flat depiction of people who might otherwise be interesting. Romantic, but not a depiction of believable humans. And the problem certainly ain't the actors.
I've never read the book, but perhaps this criticism applies to the book as well. King certainly has a tendency to push fetishized characteristics that take the place of earnest characterization. This is certainly true of the Stand, the Dark Tower series, the Shining, Insomnia, Green Mile, and probably many others of his works. This is not an original take. See one popular opinion here: http://strangehorizons.com/non-fiction/articles/stephen-king...
I like the movie, it's one of my favourite films of all time, and I am sorry you feel I and a large contingent of people are misguided because they have a different opinion than yours or your favourite critic's.
I have rewatched it in the past 6 months BTW.
One example of a truly unfilmable King/Bachman novel is Thinner, though maybe it could now be done, at great expense, with AI (there was a ridiculous TV version, though).
I interviewed him, when I was aged 16, in 1983, and asked him about The Shining. He was in a conciliatory mood on the topic that day, but re-emphasized how little he thought of Kubrick's shot choices for the scene where Danny discovers Wendy reading his manuscript.
To that criticism, Kubrick responded over the years that if we had just been jump-scared by Jack suddenly appearing over Wendy's shoulder as she read, we would have felt relief and even started laughing to blow it off, which would have undermined the tension Kubrick was looking to build past this point in the scene.