I guess maybe they won't make one for star trek beyond because the script was subjected to too many changes and last minute additions while filming and doing reshoots.
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I have absolutely no inside information here, but I can't imagine that's the issue. There have been last-minute reshoots and script changes on pretty much every novelization I have ever worked on. That's pretty much standard operating procedure.
"Hi, Greg. We're faxing you the new ending. Can you rewrite the last six chapters by Monday? Thanks!"
And if the book ends up being different than the movie, because of last-minute reshoots . . .. well, again, this happens all the time. I don't think I've ever written or edited a movie novelization that matched up perfectly to the final cut of the movie . . ...
And as for novelizations based on movies based on pre-existing novels or short stories, let us never forget BRAM STOKER'S DRACULA . . . by Fred Saberhagen.

(True story: I once turned down an opportunity to edit a novelization of THE ISLAND OF DOCTOR MOREAU on the grounds that there was already a perfectly good novel of that name by H. G. Wells . . ..)
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