I've only read a few of Koontz's books - in fact, I think the three I mentioned earlier might be the only ones I've read. At the time, Phantoms and Twilight Eyes were supposedly his best. I would still recommend them now to horror fans. His other stuff, I dunno, but I suppose there's a reason why so many of his books get turned into bad direct-to-video movies. (Phantoms also got turned into a movie, but I recommend ignoring it, avoiding any spoilers, and just reading the book.)