Euggghhh!
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:
Pet Sematary
Salem's Lot
The Shining
Firestarter
Desperation
Christine
Rose Madder
Misery
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.
I don't know what it is, but something about his writing just makes me lose interest really easily. I've tried to read most of those books, and the only ones I made it through were Misery, Christine and Desperation. I'd like to try and read the other ones now, but my dad kept all my books when he kicked me out.
I don't know why, but I prefer Dean Koontz over Stephen King. I like Denis Lahane too.