I rarely talk about films as I'm not a great watcher of them, and as such I'm hoping those who are will comment here! What I want to look at is the two-way street that takes 'consumers', for want of a better word, from page to screen or from screen to page.
So, have you come to a book through a film adaptation (and let's stretch a point and include television, too), or do you have a much-loved book which you have then seen successfully dramatised? The Janeites will no doubt have both favourites and those they deplore among the screen versions of the Austen novels, but there will be many who were inspired to pick up the books for the first time by Colin Firth, Jennifer Ehle, and their ilk.
The two media must make for somewhat incompatible bedfellows, the one requiring from the consumer more imaginative engagement than the other - which is why many filmed interpretations can feel 'wrong' - but the measure is so subjective that it's not hard to see why that should be. The other side of the coin is the writer's reaction to their work in screen form; any liberties taken with the original material must be painful for them to witness! Going the other way, there are bound to be books which disappoint those who have first encountered them in a form far removed from black type on white paper.
Being specific rather than general for a moment, the film version of Cormac McCarthy's novel The Road has just been released; have you read the book and/or seen the film? And talking about going from page to screen and back again, here's The Road issue of the film magazine Little White Lies, which rather brings us full circle!