I highly recommend Enders Game. Especially if you're interested in Sci-Fi, you'll appreciate it a whole lot more. If you liked it, then read Enders Shadow afterwards, it's basically the same story told from a different point of view. The main character of Enders Game is Ender, and Enders Shadow's is Bean, but the author does a really good job of 'filtering' the story through the lenses of the eyes of the main characters. The two characters notice different things, react to the same situations differently, etc. He calls it a 'Parallel Novel', and it fits perfectly.
Enders Game is more action packed, but if you're into more of the conceptual stuff, then go read the sequels too.
Also, Touhou is what pushed me to read it but... read And Then There Were None. Yeah, I know, but its a really good suspense/paranoia/mystery book. My 2nd favorite, in fact.