I enjoyed Ender's Game well enough, but I felt pretty cheated at the end. I kept seeing things throughout the book that seemed kinda dumb and didn't make much sense, but I knew there was a twist ending and figured it would make everything fit together. Nope. The ending actually made the entire thing make even less sense.
What was the point of abusing Ender the way they did? What was the point of singling him out, of constantly changing the rules on him, and of basically making his life hell? The adults note constantly that what they're doing is going to fuck him up for life, but they make vague references to how "necessary" it is. Except it isn't. Ender doesn't know that he's committing genocide at the end--he doesn't need any kind of emotional detachment. All he needs is strategic knowledge, because he thinks he's playing a game. Nothing that happened to him previously mattered.
Heck, the reason they chose him--his kicking that one kid to death? That was also completely irrelevant. Since the entire plan revolved around him not knowing that he was commanding actual ships in an actual battle, there was no need to have a kid who saw that kind of fighting as a good thing. They just needed someone who was good at strategy. That's it. The idea that they needed someone who could emotionally connect with the bugs or whatever was complete idiocy. You don't need that to be able to be good at strategy--you just need to be good at strategy.
Also, that plan had to be one of the dumbest things I've ever come across. Take a kid, emotionally abuse him for years, then hand him a "game" that actually relays real orders to real ships on a real battlefield. Yeah, nothing could possibly go wrong there. Unless, thinking it's a game, Ender decides to just screw around (we've all done it--firing at friendly ships to see if they'll explode, flying into the sun/asteroids/planets, crashing ships into each other, etc). Or, because his teachers are total douchecanoes, he just decides not to play at all. Or decides to send all of his ships away from the battle, to see what happens. Or the pilots decide they don't trust the orders coming from a kid who doesn't even know he's commanding a real battle. The only reason the plan worked is because of author fiat.
I can understand why some people enjoyed it, but after that ending I don't think I'll be touching anything else by Card.