I've never known King to speak disparagingly about Koontz.
King called Koontz "sometimes … just awful" and James Patterson “a terrible writer” who is “very, very successful.” in his On Writing: A Memoir of the Craft novel.
You know, by this point in the Vampire Diaries book sieries Ellena had been turned into a vampire, killed, and brought back to life as a super-powered 12-winged Japanese demon (it makes sense in context) and is a pawn in various power-plays amongst members of the celestial bureaucracy. And it's still mostly just a teen romance.
The best thing about TVD show is that it only took a few names and concepts like daywalker rings from the books and ignored the rest. The books are quite bad compared to the show.