Stephen King's most faithful adaptation... for better or worse.
I read the novel version first, being the dedicated 'book-first' person I am, and wasn't too scared by it. It was disturbing, it was horrific, but only at the time. It didn't cost me any sleep, but it did freak me out a bit.
The film, however, was far more disturbing. The first half hour is somewhat slow, though it does do a good job building up the tension without making any actual horror. However, once the film gets to about 40 minutes, the horror goes from 1 to 100 quick.
In one of the most disturbingly realistic scenes, a woman commits suicide onscreen, and this scene actually forced me to shut off the film my first viewing.
The rest of the film is typical slasher fluff, yet the effects are quite capable for 1983.
A great Stephen King film, if not exactly original.