I have read a couple that apparently realized the script wasn't going to fill out a novel and just made up extraneous stuff to pad it out. On a mostly-unrelated note, I read Brad Carter's fairly recent novelization of killer bigfoot movie Night of the Demon, and I thought it was actually pretty well-done, not at all the meme gag I was expecting. He filled out the (very thin) plot of the movie with more gore, sex, and a giant conspiracy. And character development, I guess. But apparently Severin is funding a bunch of these things. I wouldn't mind reading his take on Rats: Night of Terror or Hell of the Living Dead.