Masterful writing and storytelling.
I've stayed away from Stephen King's books because I do not like being scared and I was under the impression that he wrote horror. He does. But in this book of four novellas, the horror is rooted in the normal human being's shadow (to use Jung's nomenclature). And the fact that it is exposed and played out through such exquisite writing makes it all the more horrifying. And the beauty of the writing makes the ugliness more ugly and also tolerable.
Sometimes a writer who is writing for a deep personal reason (and not all writers do) will expose his motivation. For me, King's M.O. came in this quote from the novella called Apt Pupil about an all-American sociopathic boy who gets involved with a Nazi, living incognito, in his small town:
The things that happened in those camps still have power enough to make the stomach flutter with nausea. . . . maybe there is something about what the Germans did that exercises a deadly fascination over us—something that opens the catacombs of the imagination. Maybe part of our dread and horror comes from a secret knowledge that under the right—or wrong—set of circumstances, we ourselves would be willing to build such places and staff them. Black serendipity. Maybe we know that under the right set of circumstances the things that live in the catacombs would be glad to crawl out. (250)