Ender's Game

Earth has been attacked twice by an insect species and expects a third. The response is Battle School: children taken young, put in orbit, and trained in a zero-gravity arena where teams of forty fight mock battles that stop being mock somewhere around the middle of the book. Ender Wiggin is six when they take him, and the adults running the school have already decided he is the one.

The battle-room chapters are the famous part and they earn it — the tactics are real tactics, and Ender wins by noticing that in free fall there is no floor, so 'down' is whichever way the enemy's gate is. But the book's actual subject is what it costs to manufacture a commander. Every hardship Ender meets is arranged. His isolation is arranged. The adults know exactly what they are doing to him and they do it anyway, because the alternative is losing.

It has been read as a book about bullying, about military ethics, and about gifted kids, and it holds up under all three. The ending turns on a piece of information withheld from Ender and from the reader at once, and it recolours everything before it — which is why people who read it at twelve tend to reread it at thirty and find a different book.