Actually I hate horror, I don't get why people like being scared, I don't.Honestly, I've never read one of his books just saw the movies and I agree the only one that was done well and scary and not all that predictable was The Shining. Now I did read a couple of Lovecraft's....... Gave me friggin' nightmares.......Not a big Steven King fan, don't find his stuff scary at all, typically I just find it more predictable and boring.The lawnmower man from the actual Stephen King story is a fat, hairy minion of the devil who eats the grass (and other things, like woodchucks) mowed by a demonic mower. And he does it while naked.
The Shining is the only book of his I remember being scary, but I enjoy his books. I never went into them hoping to be scared.
If you want nightmares, I recommend the short stories of M.R.James. 'Ghost stories of antiquary' Now they are scary. One was made into a film called' night of the demon'
Oh ! go on, treat yourself to an old horror film. 'night of the demon' is free to watch on the following link.