I've just revised one of my horror e books, "The Werewolf of Misty Valley." The revision made no changes to the original story, but added more scary scenes to the story, making it significantly longer (and scarier, I think.). The e book also contains a short story, "The Dweller in Big Misty."
As for the paperback version, I made the same changes, but added a second story making it a dual novella. The second story will be "Frankenstein and the Zombies." So the paperback version now contains two good horror novellas.