I don’t mean for the film studios, because for them the point is the Daffy Duck-style dollar signs appearing in their eyes. A quick calculation by SlashFilm found that only two of the top 30 grossing films of last decade were original stories: Finding Nemo and Kung Fu Panda. Adaptations are great business decisions. They come pre-hyped, risk-reduced, and with a built-in audience ranging from curious onlookers to rabid fans.

And if you haven’t read the book in question? You probably don’t care where it came from. You might feel some of the pitfalls of books-to-film adaptation – too many characters, bloated running times, plot points stuffed in until the screenplay is oddly shapeless – but you might not.

No, I’m talking about the specific sensation of watching a faithful adaptation of a book you’ve already read. For example: you couldn’t say Hillcoat’s The Road is a bad movie. In many ways, it’s great, and some of the problems I had with it were those I already had with the source material. (Yes, I’m someone who thinks that the ending is a cheat, and one that’s almost on par with “he woke up and it was all a dream…”)

I’m a book-rereader and a movie-rewatcher, so it’s not knowing what’s going to happen that bothers me. The movie of The Road was faithful enough that I knew how it would happen, too.

I’ve ranted before about how movies like Watchmen suffered from too much fidelity, and would’ve been better served by taking more chances. That would help make them more medium-specific, but it’d also give them more of a reason to exist in the first place. With comic book adaptations, it’s not enough to just get to see the pictures move. With adaptations of a novel like The Road, it’s not enough – for me, at least – to create a visual landscape that matches the one the prose planted in my head.

(Which the movie did, without doubt. It’s one of the most convincing apocalypses ever put on screen.)

So: what’s the point? Is it to have an excuse to enjoy the story again? To see how it matches against what flickered in your imagination as you were reading? To spot the small, inevitable changes to the narrative? To hear how the dialogue sounds, spoken out loud? Is it curiosity about whether or not the movie got it ‘right’? Or that the movie experience is an upgrade, flat-out superior to the one offered by a novel?

Or are the two mediums so different that you don’t feel redundancy in even the most faithful adaptation – and I should just shut up about it?