In general, a "movie tie-in edition" is simply a new printing of the original book with a new cover using art from the movie. For example, when the most recent version of I AM LEGEND came out, Tor simply reprinted Richard Matheson's original novel and slapped the movie poster on the cover. There were no changes to the text. Ditto for the movie tie-in editions of WHAT DREAMS MAY COME, STIR OF ECHOES, and THE MOTHMAN PROPHECIES by John Keel. (All of which I handled for Tor.)
Now, as mentioned, occasionally someone will put out a novelization
of movie based on an earlier novel, as with that Bond movie or, infamously, Bram Stoker's Dracula
by Fred Saberhagen. But that's a different thing. You can tell the difference by looking at the credits. If it says something like "A novel by Greg Cox based on the screenplay by Joe Blow based a novel by Charles Dickens," you're dealing with a book based on a movie based on a book.
But if it just says "by George R.R. Martin," it's simply the old book with a new cover.
Hope this makes sense!
Elaborating on the topic: Sometimes, of course, a movie is based on a short story
, not a novel, which presents certain challenges. In cases like REAL STEEL or THE BOX, which were each based on short stories by Matheson, I would put together a new short-story collection, The Box and Other Stories
or whatever, and slap the movie poster on the cover to create a new "movie tie-in" collection of Matheson stories.
I did the same thing with REAL STEEL . . . .