One of my favorite examples, which I've mentioned before, is Paul Monette's novelization of Herzog's NOSFERATU THE VAMPYRE, which, when you think about it, is a novel based on a remake of a silent movie based on Dracula by Bram Stoker.
It's actually very well-written, though!
Thank God Universal eventually dropped their plans to remake THE INCREDIBLE SHRINKING MAN as a wacky Eddie Murphy comedy. Matheson's original novel is not remotely a comedy, so I honestly wrestled with what I would do if the remake ever happened. Putting the comedy poster on the novel would have bordered on false advertising, but how do you not
put out a tie-in edition when there's a big new movie version? As Matheson's editor, didn't I owe it to him to take advantage of any opportunity to sell as many copies as possible?
(I once asked Richard, hypothetically, if he would object to me putting Eddie Murphy on the cover of his book. He sighed, but gave me his blessing.)
Thankfully, I was spared this dilemma when the movie disappeared into Development Hell!