Ender's Game by Orson Scott Card is a terrific sci-fi book.
It's about ultra-intelligent children being trained to defend the earth in a space war against alien invaders. That could be the plot of a really empty action story, but there's a lot of meat in Ender's story.
The ethics of war, the treatment of children, the brutal realities of a highly competitive childhood, the importance of friendship and leadership.
I read it and loved it. I also enjoyed the sequel Speaker for the Dead, which is an utterly different book but equally clever.
Ender's Game was always destined to become a movie. Unfortunately, between the book coming out (1985) and the movie being made (2013), Orson Scott Card has made many anti-gay statements.
To be fair to Card, he's basically reflecting the views of his church. He's a Mormon, so we can understand where he got his ideas and who he shares them with.
To be fair to the rest of us, who cares? In a pluralistic world, if you can't justify something without reference to your god, then you can't justify it at all.
