Stephen King's somewhere in the middle of those two descriptions, for a lot of his more famous horror-y books. If you want some quick thrill-ride horror, read a coupla short stories from Night Shift. 'The Lawnmower Man', 'Trucks', 'The Mangler' and 'The Children of the Corn' are all quick-read shock-horrors with sucker-punch gore. They're not taxing to read, entirely absurd, and they give a good indication of his general writing style.
Personally, I think he's far better at coming-of-age stories; Rita Hayworth and Shawshank Redemption and The Body in Different Seasons (Shawshank Redemption/Stand By Me in the movie world) really capture the human condition, and there's very little horror involved. For all its notoriety as the ultimate horror opera, IT is more bildungsroman than horror, and it captures being an outcast growing up, bullying, and school life in a way that we can all empathise with, even if the setting is inescapably Americana (which is unrecognisable to anyone growing up outside the US, save for relentless media representations of it). The horror within it is more thrilling than disturbing/insidious, I'd say (very monster-based: child alone in a deserted school gym, monster appears, frantic chase, narrow escape, etc.) but then it's a good 1,000+ pages, so best not to start with that until you feel that you actually like King's style.
Frankly, anything he wrote before ~1985 is worth reading, most stuff after hasn't been premium King.
I'm currently reading Purple Hibiscus, as I saw it in my library. It's very good so far. I also picked up Mysterious Skin and Asimov's Robot Dreams.