There appears to be three basic ways to approach adapting a book into a film. As with most things in life, the easiest way to illustrate this is through Stephen King film adaptations… The first, and most obvious method, is that of Frank Darabont with Rita Hayworth And The Shawshank Redemption (The Shawshank Redemption) or Rob Reiner with The Body (Stand By Me), which is to take a book and simply try to be as faithful as possible to the source material, leaving the dialogue and set pieces essentially in tact, making only minor changes for cinematic purposes. The second, and probably most sensible when tackling an 700+ page Stephen King novel, is that used by John Carpenter with Christine or David Cronenberg with The Dead Zone, which is to deliver a faithful, but condensed version of the book by building the screenplay around key scenes and concepts of the novel, removing repetitive and non-narrative scenes and sometimes combining characters. The final, and most interesting method, is to pick a few key scenes and ideas from a story and then build something completely new out of this handful of ideas, Stanley Kubrick did this to great success with The Shining (much to the ire of Stephen King who later readapted his novel into a considerably less interesting TV series), Brett Leonard did this to extraordinary WTF-ness with The Lawnmower Man and Stephen King himself did this and vast quantities of cocaine with Trucks (Maximum Overdrive).
Anyone with more than a passing interest in The Criterion Collection would be aware of the general commotion that occurs every couple of years when Criterion release their special edition of the Wes Anderson film before last. The whole process is always quite fascinating to follow on social media. The Criterion Collection is justifiably the most esteemed home video company in the world, renowned for not only the exceptional scope and quality of their releases, but also the time and effort that they put into packaging and supplements. As a result of the excellence of their work, the company has quite rightly built up their own rather zealous group of followers.