I saw the trailer for the movie and got super-excited and decided I'd go see what Goodreads was saying about the book, and I found a bunch of negative reviews that I don't think are really fair: 
 1) The "Oh-It's Not Literature!" Complainers: You find these reviews for every single book on Goodreads, even especially some of the greats, like The Lord of the Rings. These people are offended that this book is loved and praised by many, even though it's written at a roughly young-adult level. Get over it. A story can be good without being written by Hemingway. No, it's not "literature", but Ender's Game is a good story. 
 2) People Who Say Battleschool is "Unrealistic": The floating in space part? Sure, way to go. The distrust between the students and the adults and the hyper-competitiveness? That is plenty realistic. Trust me. (Or spend some time at a military school, your pick) 
 3) It Wasn't a Great Book About Gifted Children: I saw several of these and I was surprised. The fact that Ender is "gifted" is really secondary to the fact that he is a child. This book isn't about the struggles of being a gifted child, it's way more about violence, and authority, and trying to hold on to innocence even when violence is necessary (and is that even possible?). Or at least that's how I saw it, and how I think a lot of people in the military would see it. 
 4) It's Just Starship Troopers for Kids: This one made me laugh because I literally read these two books back to back, and I wonder if the person who wrote that read either one. Yes, both books take place in the future where humanity is fighting against an alien race called "Bugs" or "Buggers", but really, that's about it. (unless you want to go for the "coming of age" angle, but that's a boring angle). One is basically an ode to the military and military service, the other brings violence and authority into question. Both are very relatable to the military, and I've seen both on military reading lists, but they make you think about different things. 
 Anyway, this book really stuck with me, and I hope the movie lives up to it.