I read these and several others by Dean Koontz when I was a teenager. I enjoyed them then. I seemed to be far more immune to horror then than I am now. I used to actually enjoy it. I can't tolerate it at all now. It gives me nightmares and then keeps me awake at night trying to avoid them. I couldn't tell you what has changed because I haven't a clue.
Despite my issues with horror, I tried to read a novel by Koontz more recently just to pass the time. I don't even remember what it was, just something I found in a doctor's office and picked up for the brief period that I was there waiting. I couldn't get into it at all. It seemed poorly written with stiff, forced prose. I don't know if Dean Koontz has changed or I have.