Simply put, the film has as much resemblance to the book as the American Godzilla film has to the original.
The book, which is actually written by R. Chetwynd Hayes, is much better. Had they remained faithful to it, people might have had a finer opinion of the film.
The movie only has one story from the book, "The Humgoo." The other two tales either are a mishmash of two stories, "The Mock" and "The Shadmock," or aren't in the book at all (that horrid tale about the boy whose father is a vampire).
If only the filmmakers had included "The Vampire & The Werewolf," it might have done better.
As it stands, though, you won't be doing yourself any favors by watching this piece of crud. Feel for John Carradine and Vincent Price, as they don't really seem to be enjoying themselves.
Read the book.