About Enders Game, Jude, I would say, try reading a chapter or two and see how it strikes you. If you like it, keep going. I have a lot of quibbles with Card, and tend to keep saying "yes, but" while reading, but I still read nonstop.
I'll answer your broader question "what do you like about Sci-Fi?", but not while I keep losing posts when the internet cuts out. Nag me unmercifully if I don't.