I think this is a very fascinating subject,
@Emurelda. I just watched The Martian this weekend and it got me thinking about how stories are turned into movies. The Martian was Andy Weir's first novel, but only became a novel because of how popular the story was (he originally released it as a serial on his website then an e-book before it was picked up by a publisher). After that, it eventually made it to movie status. I can see why it is a movie - the book was fantastic and the movie was similarly good.
The part of the story that's missing is the in between. Who does the research on stories and decides which ones will become movies? Who looks at something like "Do Androids Dream of Electric Sheep" and goes "that would make a fantastic movie". In some cases, whoever researches the books does a fantastic job, but in others the ball is thoroughly dropped. Just once, it would be interesting to achieve "fly on the wall" status to be able to sit in on the initial pitch meeting (and the eventual chewing out meeting if the movie bombs - like Battlefield Earth did

).