If I've lost interest in a book, I put it away. Life's too short for me to spend time reading something I've lost interest in.
It's happened to me several times. My dad was a Tom Clancy fan, and indeed I rather enjoyed The Hunt for Red October and Red Storm Rising. But my dad highly recommended Cardinal of the Kremlin, and halfway through, I lost interest in the characters, put it down, and never went back. Dad was shocked. But years later, he gave me Rainbow Six, and I didn't even make it a quarter of the way through that one.
The other was a Scott Turow work. I thought Presumed Innocent was an absolutely terrific yarn. He followed it up with Burden of Proof, which was not so terrific but readable enough. And then I picked up Pleading Guilty, and by the time the character picks up a bottle and starts downing it, I was so fed up with his tiresome whining that I simply couldn't take it anymore. He'd taken a Woody Allen pill or something. And the downward sequence of readability was sort of like a M. Night Shyamalan progression: Terrific, then okay, then thud, who told this guy he could tell a story?
(If I'd only taken my own advice when reading Clive Cussler. I picked up one, finished it, and couldn't believe I got through it. A couple decades later, I picked up another thinking, "No way could he have been as bad as I remember," finished that one, and those are hours out of my life that I'll never get back. However, he is inspiring in his own way. It makes me think, "If he can make money writing that hack crap, there's hope for me yet.")
I'd suggest picking up something else to read that you know could hold your interest, maybe something you've read and enjoyed before. If you're tired of reading, you'll know that soon enough. But if the Stephen King story just doesn't appeal to you, that's okay. You're allowed to not waste your time when a story doesn't grab your interest. Move on to something that does.