I didn’t see the movie of “Intensity”, and haven’t read the book either, so I will take your word that the movie was horrific, and will probably avoid the movie-and I thank you for letting me know!!
Koontz is usually rather graphic in his depiction of violence, but IMHO, there is far worse out there(another dicussion altogether, I guess!!) and at least with Koontz the violence has some point to it.