On the comparison of book adaptations to movies, Ender's Game director Gavin Hood sums it up nicely.
"I also want to say straight-up: the book is the book, and stands as the book, and I think one must never expect, can never expect a film to be a book. The book’s the book. It’s a way of describing a character in a situation in a totally different way to the way visually things are done. It’s a little like saying if I did a pencil portrait of you, and somebody else did a sculpture. Instead of saying, “does the sculpture capture your essence, or does this pencil drawing,” I start arguing why the pencil drawing doesn’t match the sculpture. Well it’s a pencil drawing and that’s a sculpture! Let’s talk about whether each one does a good job in its medium of capturing that character."
This is such a great way to look at it. It's aways a sore subject when you talk to people that strongly prefer on over the other - I'm equally guilty as well when it comes to comparing comic book characters to their big screen counterparts. (Hey, did you know Batman's actually a detective in the comics? And can actually fight and not just punch people's arms?) I just need to take this quote to heart myself then.
The quote is from a great interview with Hood, check it out here: http://wegotthiscovered.com/movies/exclusive-interview-enders-game-director-gavin-hood/