The first forty pages or so of Strange Highways are quite promising, establishing a real sense of place in Pennsylvania mining country, in an area where underground coal-vein fires have forced the evacuation of a village near the protagonist's hometown as the ground begins to crack, explode, and subside.
However, the supernatural events, when they really start coming, quickly veer into complete goofiness. Why? Something wants our protagonist to change the past. So it sends him into the past. And it provides a magical way for him to know whether or not he's changing the past for the better. And then, at the climax, after numerous speeches in which the protagonist is guilted by another character for not Having Faith, time keeps resetting itself until he gets everything right. It's like Live Die Repeat, Now With 100% More Satan.
We're left with a hero who seems like a dunderhead. Given the supernatural events going on all around him, he doesn't really need to have faith: empirically speaking, God does seem to have been proven to exist. And two plot devices ripped from the headlines of the early 1990's -- Satanist teenagers! Repressed Memory Syndrome! -- look awfully threadbare with the benefit of hindsight. So, too, the repeated and increasingly mawkish sermonizing. Koontz is a lot of things, but an interesting philosopher he is not. Not recommended.