I love Ender Wiggin. I couldn't wait to complete the book just so I could rave about it, but at the same time I didn't want to finish. In fact, I started typing this review before completing it. I love this book that much. 
 We're in this society where the government breeds genius children for military training. If found suitable for the program, they're shipped off to Battle School at the ripe old age of six. 
 You forget that these students are children. They're divided into armies within the school, each with a child commander, and are put up to mock battles against each other in addition to their vigorous training. They're molded as soldiers at a young age so they can battle against alien invaders ("buggers") when they attack again. 
 Things change with Ender, though. Unknown to him, he's being trained as a commander from the start. The rules are broken, and the school pushes him to his limits. And because he's a genius, he prevails. But he is mentally and physically exhausted; he is isolated from his peers and misses his family terribly. It's his inner monologue that reminds you that he's a just a child. No one at the school talks about family, but he thinks of his often. And at night, when he's alone, is when he allows himself to cry. 
 The only person he ever loved was his sister, Valentine, and she's his motivation to go on. But his change in character is painfully obvious when they meet again, after years of him being away from home. When he left, he was naive and innocent. But over time he became a fighter, a soldier. Yet still a child, which she continually reminds him. We, as the reader, have witnessed this progression. But it's subtle. He is focused on winning battles as a child would, like it is all an elaborate game. But no one knows what's going on behind the scenes, and he doesn't fully understand what he is being trained for--until the end of the story, of course. 
 Ender sees himself as a killer, though he doesn't want to be, and is constantly striving to break free from it. His character development is real. We know what he's feeling, what he's struggling with, and when he wants to give up. We know what, and who, he loves (and hates). And this all works together to help him grow up. 
 There is so much more in this book that I haven't even touched upon. Just read it. If you care about science fiction at all, this has to be bumped to the top of your to-read list.