I love both film and books. If you go to watch a film version of a book, what do you hope it to be? A word-for-word adaptation- basically a visual translation? An interpretation? A film with the same story but with different twists? A tauter version of the story?
In short, what do you want a film adaptation to be?
Ahhh...that's a different question. None of the above. I hope an adaptation is true to the spirit of the novel. For instance, the movie version of "How to Eat Fried Worms" has a completely different plot from the book, but I love it because it's in the same spirit and is about the same things (not worm-eating, but rather the importance of honor, respect, and hierarchy in a pack of little boys, and the lengths they will go to for those things).
On the contrary, all the movies based on Philip K. Dick novels are awful (except for Total Recall, Bladerunner, and A Scanner Darkly!) because they aren't at all in the spirit of PKD's writing. Instead they are in the spirit of a dumb action movie with a testosterone-laden alpha hero running around with loads of stuff blowing up.
What do you think the purpose of a film adapted from a book is?
To tell as faithful a version of the story as a completely different medium allows.
To make a profit for the producers.
I think the purpose is to tell the story using a visual medium. To allow that medium's creative minds, director, producer, actors, costume and set designers, and so on, to interpret the story and create an entertaining piece of art in its own right.
I want a film adaptation to be an interesting and entertaining film. I used to be all about adaptations being as close to the books as possible. Now I have a different view. I've seen some adaptations that made changes I liked and thought worked well for the story. Basically I've come to think of the book and the film, even if related, as separate. It's true the center of the story should stay the same but generally I try to evaluate each on their own rather than judge one by the other.
What I mean is 'What would you like from a film adaptation?' Do you think that it's sacriligious or does it intrigue you?
What I would like from an adaptation is for the film to be as faithful to the source material as practical given time constraints and the current state of technology. I'll settle for the movie not butchering the story it purports to adapt.
Consider the 2002 adaptation of The Count of Monte Cristo. The movie was a complete butchery of the novel in that it had Edmond Dantes achieve his revenge through swordfighting and had him get back together with Mercedes at the end. However, if the movie had just been called Cleavage and Swordfights, it would have been frigging awesome.