Having seen the film before I read the book, the reduced role of the secondary characters was an unwelcome "change" to me as well. IIRC Carl doesn't get much to do in the novel, whereas his role in the film I find enjoyable...especially given the "hey, it's Doogie Howser!" aspect.
As far as I'm concerned one of the big reasons The Godfather movie is so great is because Coppola knew what to cut out of the book. There are whole sections going on and on about how Sonny's mistress has an oversized vagina and since Sonny is so large he's the only guy that can satisfy her. If I remember right, that's actually one of the closing scenes, her getting an operation from her new gynecologist boyfriend to fix that. My god that was awful.
As Greg said, the horror stories are more fun to tell, but I have as many pleasant movie novelizing experiences as horror stories. While it had a compressed timeframe (that wound up being unnecessary, as the movie's release was pushed ahead five months a day after I turned the book in), writing the Serenity novelization was a joy and a privilege, the producers of Darkness Falls were hugely helpful in providing me with backstory and script changes (they even showed me and my editor the changed ending so I could work it in), and for the third Resident Evil movie I got carte blanche to expand on it and bridge the gap between the second and third films and also provide a subplot for a character from the second film who wasn't in the third due to the actor being unavailable.
Most of the "horror stories" simply involve the basic challenge of trying to write a 300-page description of a movie you haven't seen yet, which is probably in production at the same time you're writing the book, and dealing with various last-minutes changes. ("We shot a new ending, so we're faxing you the revised script pages. Can you rewrite the last chapter by Monday?") On the fun side: Kevin Grievoux of the UNDERWORLD movies once let me pick his brains over the phone regarding the backstory he had invented for his own character, which I worked into one of my novelizations. And there are worse ways to spend a day than hanging out on the Warner Bros. lot checking out the costumes and props for MAN OF STEEL . . .
Never. Occasionally there's talk of it, and I've heard rumors of such things occurring once in a blue moon, but, in my vast experience, it never happens. In terms of visuals, you're usually working from some pre-production art and maybe a stack of publicity stills. Edit: Okay, on Death Defying Acts, I was sent an advance copy of the movie trailer, which I watched over and over, taking notes.
On the other hand, the screenwriter has already done most of the heavy lifting when it comes to the plot and dialogue. My job is just to figure out how to translate the (unseen) movie into prose. You also have to be able to check your ego at the door and remember that, ultimately, you're trying to do justice to somebody else's story . . . as opposed to trying to put your own stamp on it.
I started reading through bits of movie scripts for the first earlier this year, and I was actually amazed at just how much description there was. I had always they were mostly dialogue with just a few vague stage directions every now and then.
It varies. Sometimes an elaborate action sequence will be described in painstaking detail; other times it will be more like "she kicks their butts with lightning-like moves." And just because something is described one way in the script doesn't mean that the art director or the special effects guys or the costume designer or the casting director or the fight choreographer won't decide to go another way on the actual film . . . . This can lead to surprises when I finally see the movie: "Hey, nobody told me that character was a woman!"
One of the reasons why I was so grateful to the producers of Darkness Falls was because -- when they showed us the re-done ending -- we also learned that the doctor described as African American in the script was cast with a white guy. Oops.
One of my favorite quotes from Ian McKellen's annotated screen play for Richard III is when he describing how they were tying to figure out how to stage the final fight from his vague script and he added:
My favourite of the "lack of description" variety of screenplay action is from the Live And Let Die, where the whole ten-minute speedboat chase centrepiece is described as "Scene 140- The greatest boat chase you've ever seen in your life."
Occasionally, you might get what TV Tropes calls a 'recurrsive adaptation', where a movie based on a book subsequently gets a brand new novelization based on the movie screenplay (often times this novelization is not written by the author of the original book, either). That's when it starts to get confusing, but thankfully it's happened relatively few times that I can recall. (In fact it did happen once on Star Trek. Larry Niven adapted his TAS script "The Slaver Weapon" from one of his previously published prose stories, and the TAS episode was then subsequently novelized by Alan Dean Foster as part of the Logs series of novels.) For the most part though it's definitely far more common for publishers to simply put out a new edition with the movie poster for the front cover and call it a 'Movie Tie-in Edition', even though the actual text of he book has very rarely been altered in accordance with that. Not saying it can't happen, but it seldom does.
In such cases, there's never any talk of revising the text. You either do a novelization of the movie script OR you reprint the original book with a new cover, but I've never known anyone to revise the original book to fit the movie . . . .
Although Arthur C. Clarke's 2010: Odyssey Two was written as a sequel to the movie version of 2001 rather than the novel version (in which the Monolith was at Saturn rather than Jupiter). And that wasn't even a movie tie-in per se, since the movie 2010 came out years later. Also, Gary K. Wolf's original novel Who Censored Roger Rabbit? was set in the (then) present day and depicted the toons as comic strip characters, but his later sequel Who P-P-P-Plugged Roger Rabbit? was based on the very different movie version, with the original book dismissed in passing as a dream Jessica had. (Though how a character in the 1940s could have a dream set in the 1980s is beyond me.) If the movie is better known than the book, and it usually is, then it's good business to do a sequel to the movie instead of the book.
Good point. Logan's World, the sequel to the novel Logan's Run, didn't literally ignore the first book, but very quickly advanced the plot so that the beginning of the sequel more or less synched up with the ending of the movie. Like in about five pages or so . . . . On other hand, Stephen King's new sequel to The Shining is very much a sequel to his earlier novel, not the Kubrick movie version. I read an interview with him in which he acknowledged that this is likely to confuse some readers who are more familiar with the movie, but he's still treating his own book as canon as it were . . . and who can blame him? Here's a potential confusing situation. The TV-movie The Night Stalker (scripted by Richard Matheson) was based on The Kolchak Papers, a (then) unpublished novel by Jeff Rice. When the TV version was a huge ratings success, a tie-in edition of Rice's novel was finally published--under the title The Night Stalker, of course. Later, when Matheson scripted a TV-movie sequel, The Night Strangler, Rice was tapped to write the novelization of the sequel to the movie based on his book! Got that?
Classic 1970s British cop show The Sweeney had tie-in novels based on the original concept rather than the actual show. The story goes that after the creator of the show and the man hired to produce it had creative differences, the creator walked. This meant the tie-in novels (which he supervised) were wildly different to what the series had done with the same characters and situation. Of course, they were published with photos of lead actor John Thaw on the front cover, even though the phrase "TV Tie-In" was a loose description at best...