I've read all the Ender books published to date and I disliked the movie greatly. I don't know how that project got greenlit, it was lazy filmmaking. As somebody said there was no progression. And Ender didn't really seem that much smarter than the other kids. I have countless other issues with it but they spoil the movie. Let me just say that there is a difference between leaving something out from the book, and then changing something just because you don't know what role it plays within the story. I really want to discuss this stuff but don't want to ruin the movie for people.
And to someone above, speaker for the dead, xenocide, and children of the mind are some of the best scifi books. Heavy in philosophy, but so mind blowing.