Ender's Game by Orson Scott Card

This is at least the sixth time I've read this. This used to be my all-time favorite SciFi title, I think I'm at the point where I like Ender's Shadow better. The only books I've read more than this one are the Bible and Jane Eyre. What is it about a certain book that can make it just as enjoyable upon multiple readings as it is the first time through? I have such a huge reading stack right now that it's hard to believe I took the time to re-read this! Onward!