There was definitely a movement happening in the early 1970s, where we saw mainstream comics publishers try their hands at paperback editions featuring prose stories and spot illustrations--y'know, just like real books!
Marvel did a book called Haunt of Horror(they also did a b/w magazine with that title), and DC did this, a paperback edition of the House Of Mystery. I had never seen this volume before, but when I saw this awesomely creepy Berni Wrightson cover, I couldn't say no(well, I could have, I guess--I just didn't want to!).
The book features eight prose stories, all by Jack Oleck, about twenty-thirty pages each:
"Chamber of Horrors", "Nightmare", "Collector's Item", "Born Loser", "Tomorrow, The World", "The Haunting", "You Only Die Once", and "Act of Grace."
Each story also features a sweet full-page illustration by Wrightson, and as you can see he was in his element here, doing some of his best work(and that's saying something!):
...there's also a nice opening page piece featuring Cain, the only reference to the comic's host in the entire book.
I don't know if these stories were ever adapted into comics(before or after), but it does make for a nice spooky collection of tales.
DC did do a second volume, but I think that was it. I don't remember ever seeing an ad for these in the comics themselves, which seems odd to me.