Stephen King’s fiction recommendations (he frequently touts books that he likes) have been mixed in the past—at least in my experience. Publishers often ask King to give blurbs and endorsements; and that tends to skew things.
That all said, I learned about the work of the late William Gay (a Southern Gothic writer) through King’s mention of him. Gay doesn't have a large body of work; but everything that I’ve read from him has met my expectations, and then some.
Stephen King, for all his faults, legitimately cares about the integrity of fiction. I don't believe that he would allow his name to be associated with a real turkey of a novel.