In Enders Game they cut a lot from the novel. As a book, it is not terribly long, and it's a very quick read. What makes the book great is not so much what the characters do, but why they do it and how. So while the movie conveys the majority of what happened in the book, it fails to show the reasons behind what they do. I do not know that they could have done better within a two hour time limit. The movie starts with the central to Ender's time at home is the central of conflicting emotions running through him about his monitor, his family, and his place as a Third. The film rushes through it, hitting each not enough to show the viewer that there is something more. Ender (Asa Butterfield) mentions being a Third, but doesn't explain what a Third is, or why it is a point of shame and embarrassment.
They introduce Peter, but fail to show that their relationship is more complex than your typical sibling rivalry. In the book, Peter is brilliant, intuitive, and a good actor when adults are around. In the movie, he's just a jerk for a few seconds before Ender rockets off toward space. Even Ender's early fight with Stilson loses much of its effect. In the book, it really isn't much of a fight, and Ender immediately has Stilson on the ground. The point of the scene was to show Ender's fighting to secure safety from the larger group of bullies. He's reluctant, but not hesitant. In the movie, this is distilled down to a shout for Stilson to stay down before the fight has concluded and a shaky warning to the others.
The commercials for this movie did not help it much, either they left the feeling that Graff (Harrison Ford) was almost a main character. Once on the training facility in space Ender finds that kids who are as aggressive and competitive as a group of adults. They are not kids in their minds, but young people who have been chosen to save the world. While capable of defending against violence, Ender tries to use his smarts to move ahead and avoid fighting. Also the movie does not show where he met everyone, and Bean is somehow in the same initial launch group as Ender, and simply serves as an ally.
Peter and Valentine just serve as some encouragement for Ender growing up, and that also means that there is no mention of Demosthenes and Locke at all in the movie. Petra has more interaction with Ender than anyone, but it has some weird romantic overtones, and I do not know why because they were nothing but friends in the novel; Petra even had her own army in the book and never did in the movie. Alai was Ender’s first friend in battle school in the book, but in the movie Bean is. Alai always talks about peace, but in the movie he mentions it, but doesn’t really do anything to keep the peace. In the book Alai kisses Ender and says salaam, and it creates kind of a feeling that Alai wants to keep him safe, but in the movie not so good acting leads to it feeling like he just says it. Alai doesn’t even kiss Ender he just says salaam and leaves.
In the movie Graff is always saying he isolated him, but Ender is always surrounded by friends and Graff somehow considers that as isolation. I don’t know what mental problems Graff has to think that as isolation, but it’s beyond me.
The director did an overall good job in this, he made some choices to make the movie less than 6 hours long. Some choices I think should have had in it, but over all he did well. It’s also well that he doesn’t let anyone get lost in the crazy world of Ender’s Game.