I've picked up the book sorta by mistake - it didn't occurred to me that a writer with a name like "Manly Wade Wellman" could have TWO characters named "John", both of whom have tendency to deal with supernatural (in fairness, Mr. Manly seems to have a whole lot of protagonists, operating in similar fields of paranormal & occasionally meeting each other).
There's a lot of "didn't aged well" elements to the stories, and even more of well established in modern age tropes, presented as "twists", but.. I found myself slowly getting hooked, there's much more research, than usually you would find in short stories like this, written between 1940 and 1970s, for example, and not all of it aged terrible.