I've always thought that the central technical challenge in writing speculative fiction is how to get all that back story across to the reader in a way that feels seamless and unobtrusive. I don't think the problem has ever been really solved. Of course, you can always just whack in a large passage of straight exposition, but I think most writers would consider it cheating, and the received wisdom is that readers will get bored wondering when the characters are going to show up. Not much subtler is to include excerpts from a future history textbook, or even to have the protagonist sitting a history exam which helpfully fills in the reader on what's been happening over the last hundred years (I seem to remember Thomas M. Disch doing this is in the excellent
334). Most speculative writers nowadays seem to try and sneak in clues here and there in dialogue and passing references to the imagined future past ("Professor, you know as well as I do that before Man interbred with fruit bats we were incapable of flight"). The more confident just charge straight in with a barrage of invented slang and technical jargon and expect readers to keep up.
