I've read every Steven King book. They all have varying levels of depth, but they're all very well written and immersive. I think everyone here had a reasonable point about a lot of his endings turning out fast and dark.
You may not enjoy this if you like stories that feel like they come to a proper conclusion, but I think that's where he excels at making his stories feel dark. The endings are almost always NOT satisfying. They often hurt.
Another thing people don't like about him is that he's a period writer, so lots of his writing is filled with current events from the time when he wrote the book. This makes a lot of his older books feel really dated (like Tommyknockers). But it's good for me.
Also, like most people who have also commented, i recommend starting with his short stories, and his more popular works. They really are good.
Recent colonoscopy here, can confirm the "grown man worth of shit" estimation