Wolf comes up with an interesting horror designation that I haven't seen before, as 'wet' vs 'dry.' If you read much horror, you get it; MR James is dry, dry, dry. And Clive Barker is wet, wet, wet.
I think the 'wet' horror in this book is the weakest. And there are a couple of weird inclusions, like the Biblical story of Jael and Sisera; you'd have to work pretty hard to introduce much of a frisson in the story as it stands (the reality is obviously horrifying).
But the bulk of the book is old classics, like The Lottery, It's a Good Life, The Fly. The Yellow Wallpaper. And horror classics are classic for very good reason - because they are AMAZING. More than any other genre, horror has to be masterful to even be good; Wolf did a reasonably good job of selecting material that should and will last.