There's a piece of advice for crafting a good science fiction novel: Don't use just one big idea, but instead three, in layers. I think this came from Octavia Butler, but it could be Damon Knight. Anyhow, Beggars in Spain, while throwing all sorts of future developments into the plot, really brings only one new, arguably small, idea. What if certain people in the near future don't need to sleep? Sometime in the 21st Century the full mechanism behind sleep is discovered, and a genetic therapy develops to greatly reduce or eliminate the need for sleep -- but it's rather difficult and expensive to perform. Not much more powerful genetic engineering than that is developed (at first anyway,) but it's enough to cleave society into the "Sleepless" and everyone else. What could you get done if you never needed to sleep? Over a couple of generations the Sleepless leave everyone else in the dust economically. It's not so much that the rich and powerful get the best genetic treatment for themselves, as it's that this treatment creates a new class of the rich and powerful, and everything comes apart. The ideas in this book stayed with me like few others. There's a kind of law of parsimony at work: Don't throw all the biggest outlandish biomedical and cybernetic developments at us at once. Just add one, and the rest will follow. Eventually we get post-scarcity, more superhuman intelligence, and eventually, near total anarchy.