Looking for a late 80s novel set in a post-apocalyptic age.
The apocalypse has recently happened, so people remember the old world. I think the apocalypse was that large amounts of the population just lost their minds and become not zombies but just dysfunctionally out of touch.
I remember the main character's wife was half-infected; she could function normally, but she always tried to kill him after sex, forcing him to lock her in a padded room. I remember also he had been a sheriff or police office.
The antagonist was his former partner (I think). I remember the antagonist crept up on a line of men walking through the woods and killed them one at a time from behind.
Most of all, I remember the book had a blurb from Stephen King on the cover, saying either it was the scariest book he had ever read or the author was the future of horror.