Generally tie-in editions are just the original book with a photo/poster from the movie or show used as the cover art, in order to promote the book to the movie/show's audience.
Yep. I know I saw a James Bond movie tie-in once ("The Spy Who Loved Me") that was a wholly new novelization by Christopher Wood. Obviously it varied enough from the Ian Fleming novel to warrant a new version. He also wrote "James Bond and Moonraker", a variation on the original.
There's also been a SF fantasy movie that has had two
different novelizations of the same movie. Can't recall which movie series, though.