Every book is special. I guess that if there are lovers of some book-books and they have money, they will be able to film it then maybe it will not be totally like a book, even with some changes but still it will be an alternative version. Books are always much bigger than films. People are not always able to read the whole book, so they decide to watch the shorter version, and if they like it, they will read a book and compare. One of the problems that films are mostly made with Hollywood shine and if a book was written many centuries ago and a film was filmed in 2013-14, it can have a lot of those Hollywood clichés.
According to this film, Pammela did not want to film her book and when she already agreed she started controlling a filming process to prevent Hollywood clichés from destroying her book. She wanted to keep everything like it was in book. But times went by, memories surfaced and she decided to soften her opinion. The Film makers changed the end, and Pammela liked it to tears.
So I guess that everything depends on a producer and film makers who either make another masterpiece or make such an awful trash that people will not even read the book.