I remember reading Ender's Game as a kid and loving most of it, but being put off by the weird dream sequency/ computer gamey bits. Coming to it as an adult, I see that while Ender's Game can be read by kids, there's a lot more in it for adults. Of course there's the moral question of using kids as soldiers - Kony 2012 anyone? - but what I most enjoyed was the finely balanced characterisations, particularly of Ender and Graff, Principle of the Battle School. Ender is a monster, but details of his actions are withheld from the reader to enable us to grow to know him and empathise with him before we realise just what he's done in the past. And Graff is another kind of monster - one that makes monsters - but again we empathise with him as doing what 'must be done' even if he personally despises himself for it. From a writing point of view it's a very skilled novel.