Stephen King books are hit and miss depending on who is adapting and directing. If its Frank Darabont, who directed Shawshank, Green Mile and The Mist(best non-hollywood ending in a Hollywood film ever. Fact!) It is good and better than the book, although i got more emotional with the Green Mile book. Anything else is generally a bit rubbish. Notable exceptions being Stand By Me and The Shining.
Some of the made for TV adaptions have been quite good though, but don't have the budget to realise Kings vision. So both It and The Stand started off very well, but fell apart when they couldnt realise Kings endings.
Sorry i am a bit of a King geek outside of Terry's world.
I also agree with Forrest Gump being better than the book.
"Generally speaking, when scary things get scared - not good."