It's really best to think of movies and books as completely different things ... because they are. However, people's attitudes towards a film's accuracy to the underlying story is hugely influenced by how good a film it is. If you look at The English Patient, a film and novel beloved by some, you will see that the two are VASTLY different ... yet both are very good in their own way. And they are thematically and stylistically similar. This is a very well documented adaptation with Walter Murch, the film's editor, having written a book with the novelist. Anyway, you very rarely hear any griping about the difference.

The first several seasons of Game of Thrones is similar (before the screen writers ran out of novels and enthusiasm for the series). There were significant "differences" (though it was clear that they were doing their best to stay accurate) but few complaints because those seasons were very good. However, make a crappy movie and you get a lot of complaints about it not being "the same."

As you can see from my notes above, sometimes making a good movie is not in the cards. Many are cursed from the beginning or have underlying flaws which sometimes could have been repaired but often could not.