In this sci-fi book Earth is at war with the "Buggers" an insect-like alien species that has attacked Earth several times. Ender Wiggins is a brilliant six-year-old boy with a sadistic older brother Peter, a loving sister Valentine, and parents embarrassed to have three children in a society where two is the norm.
Ender is given the opportunity to attend Battle Academy, a space-based school where children are groomed to be military officers in the war against the Buggers. Though Academy students must leave Earth and their families for many years Ender decides to go. The commanders of the Academy believe Ender might be "the one" who can defeat the Buggers and purposely make his training very difficult. Even when Ender is the target of jealous bullies he is left to handle his problems by himself in the hopes of shaping Ender into a superior self-reliant officer.
Most of the book describes Ender's training at Battle Academy where combat strategies in zero gravity are learned. Ender is a good student and even helps train his friends, all of which leads to a strong militia. Any more description would contain spoilers so I'll just say the story has some interesting characters and a few surprises.
For me the repetitive scenes of battle training got a bit old but I think a lot of people would like this book. There's also a movie adaptation.