Ender's Shadow is a mixture of several genres. It is partly sci-fi, partly dealing with the psychological experiences of characters, and partly a children's book. The reason for the last is that unlike in most sci-fis, the main character is a small kid - much more mentally developed than others but still a kid - and events such as a war against aliens are looked at from his perspective.
Related: Ender's Game
Ender's Shadow is a science fiction book that can really make you stay awake all night because you can't stop reading. It has the story of Ender's Game, a book I have previously recommended, but it is told through the eyes of a totally different character, Bean. Without him we understand that Ender himself would have never managed to succeed in his mission. I recommend it not only to fiction lovers but to all people who want a dynamic and interesting book.