I have searched for this book for years. I checked this hardcover book out of my elementary school library twice in the early to mid 70s, when I was in 1st - 4th grade, as far as I can remember. I don't remember if the stories were by different authors or not. The story I remember best was about a boy who had a puppy.
His parent(s) brings home something they found or dug up, it was a bundle of bones, like a mummy. It was placed in a dark cellar or basement, I remember a scene where the puppy goes down where the "thing" is, and is killed or injured, and boy goes down after the puppy, and I believe the boy also comes to a bad end. I think there may have been another story that involved vampires or something like it. There were sparse illustrations, I believe.
I was never able to read more than a couple stories, the book scared me too badly at my age then (I remember hiding the book when I wasn't trying to read it). It seemed very scary for a children's book, I don't think the stories had happy endings.