A full book? Urg. Despite hearing that complete books are easier to write than short stories, I'm still a bigger fan of the short story. Or possibly novella. I never really understood what that was. However, if I did write a full book it would probably heavily draw from Terry Pratchett and Douglas Adams's style in a futuristic alternate universe. Despite my love for more serious literature undertakings, I don't think I could ever be so bold as to claim I would be able to write something as profound as Hyperion or as in depth as Cryptonomicon, but that's precisely what I'd want to do. Though even saying that doesn't do justice to Pratchett's amazing insight to human nature and ability to write, or Douglas Adams's... well, OK, since then I've felt he wasn't quite as significant an author and if I had read his books now they wouldn't have had the impact they did when I was younger, but I still feel he left an important mark. Plus I would HAVE to write a humorous book, even if I turned out to be terrible at it.
Anyway, it would be a sci-fi comedy set in a distant future of an alternate universe.
Either that or I'll just rewrite Confederacy of Dunces and call it a coincidence.
EDIT:
In more of an actual answer to your full question, It would be a theme of futility. I love the idea that no matter how much of an impact you think you can make, it's still just throwing pebbles into the sun. I have no idea about any of the other things you asked, that's thinking way too far ahead for me.