So it's not high literature–well, actually it is, in comparison to the other Koontz novel I've read (I swear, it's about a genius dog and and dog made of pure evil and it sah-ucks)–but it's summer, dude, relax.
Intensity is a wet dream for women who watch and read about true crime; coming up with ways they themselves would escape from maniacs and the like. And yes, I am one of those women. Sure, it's a bit contrived and it's been done before, but parts are actually “intense” as the title and weird but pretty cool cover art would have you to believe.
I also remember seeing an entertaining TV movie adaptation years ago, but it's not readily available.