Ha, obviously! Duh, of course! Not trying to sound condescending. : ) How else could they get the content and material?
I mean... perhaps in special circumstances when there was no book to begin with and there was just a very, very successful original blockbuster hit. Then they can commercialize the s-h-i- t out of it, there becomes a ton of merchandise created pertaining to it. Depending on how popular it got, they can think of pretty think of anything to sell, slap the copyrighted name onto it to draw in a large profit. So they figure can get even more revenue yet from fans interested in engrossing new plot lines involving their favorite characters.
But I don't think it is always as superficial as I made that sound but in most cases I can remember, it goes something like that. That's just smart advertising and consumerism in our capitalist society though, I guess.
You know, so taking advantage of a movie's success. Some examples I can think of is like Star Wars which became an epic phenomena and cult classic. It became a huge part of American culture. They wrote follow up stories and some graphic novels I believe. In these cases they usually just try to continue the story in a setting of the lives of the characters post whatever events occurred in the film.
But a lot of die hard fans of the movie(s) can end up hating the direction it develops towards and disagreeing with choices the author makes in epilogues. It like ruins the novelty and nostalgia and deep connection that might have been there from the original(s). The good thing is that it doesn't necessarily have to be true in their hearts, minds and imaginations of the story. You can take it or leave. At least that's my opinion.
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