I've disliked almost every book King has put out since the mid-2000's. Duma Key was an exception. I didn't actively dislike Duma Key, I just thought it was extremely mediocre. What made King great, in my opinion, was the breakneck pacing of his books. His best books wasted few words, but the older he gets, the more he drifts from that concept.
The Dark Tower series is the best example of this, because they stretch from near the beginning of his writing career until the mid-2000's. The first three books were great! They we appropriately lengthed, they didn't waste any time telling the stories they set out to. That's King at his best! However, each book past that point gets longer, windier, less succinct. Still entertaining, but still disappointing for their sloppiness. Beyond that, nearly every King book I've picked up has either been sloppy and uninspired, or simply a bad remake of one of his older, better books (Especially Cell and From a Buick 8).
You want King at his best, try:
Some of his Bachman books are pretty good, too. The Long Walk and Running Man were both fun reads.
A lot of people disagree with me, but it's just my opinion! I'm not saying you shouldn't enjoy them, just that I don't.
Lately, I've been working through Christopher Moore. He's goofy, but his books are a joy. They always make me feel warm and smiley, and there are some good laughs to be had throughout. Here's what I've read over the past week or so:
The real story of Jesus, told from the eyes of his best friend, Biff.
An ancient man-eating demon named Catch, and his 100-year-old master, are wreaking havoc on a tiny coastal town.
A Native American criminal-turned-insurance-salesman finds himself dragged back into the world of spooky medicine magic when the indian god Old Man Coyote, the trickster, shows up to fuck his couch.
King Lear, retold with a lot more sex, murder, and codpieces.