A story about a gifted child plucked from his family and allowed to become a military commander to save the earth from an alien species with which two battles have already been fought.
The story has received criticism because Ender can commit any act of violence he likes but he always remains morally clean - do the means always justify the ends? This is actually a misreading of the story. Ender always expresses great remorse for any time he hurts anyone. The path that Ender takes at the end of the novel is dictated by this remorse.
One problem I had with it is that the side story around Peter and Valentine and the civil war at the end seem tacked on. Orson Scott Card originally had a story about the Speaker for the Dead and wanted to pen a back story for the character. The other plot elements were added as filler/linker plots and I think it shows. I don't like the direction the novel takes after the last battle. It feels very rushed, as if he is trying to set up his next novel before we get bored after the main action has finished. I don't think I'll be reading on in the series.
The parts that I enjoyed the most were about Ender and his journey to the final battle. His amazing abilities and genius level of understanding of strategy are very convincing. The way that he starts off as a bullied small kid and finishes as the top kid in school and the way that he teaches himself and does not follow a prescribed school curriculum.
All told a worthy winner of the Hugo and Nebula awards and an enjoyable read albeit one with some filler/padding/linking.