No, I think of Mr. King's works as finely told stories of some adventures of his finely-drawn bigger than life characters who may or may not be in some very unusual situations. Yeppir. Big hugs, Mr. King, big hugs!!
I was once reading SALEM'S LOT by myself at home. Dead silent in the house and the sun had just gone down. The phone rang, and I jumped to new undiscovered heights.
If you let King suck you in, you'll get your scare.
If I'm thinking of the same definition as literary as you are (and I probably am), let me say, yes, I agree, he can write in that manner, but I think he mostly chooses not to, and I think the majority of his prose is decidedly non-literary, the so-called Big-Mac/fries analogy. That's what made him popular, I think. However, one might argue that some of his more recent stuff, especially perhaps some of the shorter tales, leans more toward that style. Granted, there are probably passages in 'Salem's Lot and It that are very literary in style, but somehow, even they come off as appealing to a wider audience than the literary genre implies (I'm thinking in particular of one example: the section in 'Lot about the town knowing darkness...there's both a New Yorker-quality about it, and there's not, the equivalent of a Schrodinger's-Cat collection of letters).There's often a literary quality
Interesting question(s). I can't say I've ever been seriously scared by anything SK has written - disquieted, certainly, but not scared in the truest sense. Off the top of my head, I'd say the closest he came was in Pet Sematary.
Does that mean he's failed in his 'quest'? Not at all, because I'm pretty damn hard to scare anyway and his stories have touched me in other ways. (I agree on the point re: is it even possible to scare someone with a book. You can certainly create tension or even unease, but genuine horror, fright? I have my doubts.)
Is he a horror writer, though? Well, yes, in the sense that much of his work wears the robes and follows the tropes of horror (though not always too closely!)...but that's not all he is. There's often a literary quality about his work that some writers of literary fiction (which is, after all, really just another genre) would kill for a tenth part of.
For me, SK is primarily a writer who captures ordinary people wrapped up in extraordinary events. As such, he gets to one or several essential truths, and his worst 'bad guys' are usually human (arguably the worst 'bad guy' being a woman), and so to a greater or lesser extent his work sits outside of the mainstreams of genre.
If you like, his stories bend genre(s) to their (or his) will rather than allowing themselves to be bent by the rules and restrictions of genre, and it's for that reason that I think SK will go down as one of the great American writers - and a key figure in the English (language) literary canon. (Where 'literary' is used in the broad sense of 'all literature', rather than the more narrow one of 'writer of literary fiction' - if there really is such a beast. Even Austen was basically a writer of romance. )