Thanks! Though right now I'm slogging through a real tome.

Holly doesn't have any supernatural horror; the horror is all what men do to men, so you should be fine. And, yes, there have been other books with Holly in them. The Mr. Mercedes trilogy, which doesn't have a lot of horror. And The Outsider, which does. I think The Outsider is my favorite of the books where Holly appears (lots of horror,) so probably not one that you'd enjoy.