I carry around, in my head, a long list of books I ought to read. The list of seminal science fiction books I ought to have read but haven't dates back to when I was 12 or 13, when I was first getting into genre fiction. The list in my head was almost entirely composed of things I had seen on Prisoners of Gravity, which I watched diligently every week. Almost all of my SF education came from Commander Rick's clandestine broadcasts.
I am pretty sure that was where I first heard of Orson Scott Card and Ender's Game. It feels like one of those books that I have known about forever, although now that I have actually read it, I realize I hadn't really known anything about it. I probably stayed away from it thinking it was hard, military SF, not the squidgier, character-driven "what if" stuff that I generally like. Whatever the reason, it took almost 20 years —and the intervention of a friend— before I finally sat down with the book.
I'm not sure if Ender's Game was specifically written for a youth audience, or if it got coloured as a book for teens because of the age of the protagonist. In many ways, it reads like a "young adult" title. It's a quick read, not the kind of book in which you need to spend time savouring the language or pondering character motivations; it's straightforward. This isn't to say it's an insubstantial book. There are some very chewy ethical issues that present themselves, but even if they don't interest you the story moves forward in a compelling way. The book works as a superficial read, and as something more ponderous.
In the future, aliens have threatened Earth, and though we won the round, it was not a reassuring victory. The military machinery is hard at work, trying to figure out how to make the victory permanent, how to protect the planet from the inevitable second round. To do this, they turn to children. The goal? Find children with the right temperament and sufficient intelligence that they can be molded into soldiers in an army that can win decisively. Unlike his siblings, who were too empathetic and too sadistic, Ender turns out to be the most promising candidate seen by the top brass. The book follows him as he is taken away from his family and trained to become, well, all that he can be.