The Dark Tower story is easily his best work. It spans seven volumes...the first (The Gunslinger) written around '76, and the final book (The Dark Tower) released in 2004.
Elements of the reality he envisioned, often intertwined with our own, can be found in the vast majority of all his writing. King is my guilty pleasure reading...there's little he's published that I haven't read. His short stories (ever see Creepshow?) are some of my favorites...I've read them several times over.
yeah creepshow was freaky...the one where the doctor buried them in the tide pools was cool and they came back covered in seaweed
but one of them *REALLY* freaked me out...it was called "The Crate" it was the one with that monster found in the box from the arctic expedition. that was under the stairs in the science museum. it was like some freaky monster/baboon...that thing scared the living fuck out of me as i was young when i saw it, and had nightmares about it for years.