Diaspora by Greg Egan
The opening chapter alone is worth the price: the Orphanogenesis chapter is one of the most beautiful and imaginative pieces of hard SF ever, the birth of a software consciousness where we see one of the main characters get iterated into existence as a software entity in a post singularity society, and there is something extraordinary in watching how human-like minds are created in a transhuman world, alien and tender at once. This is no-holds-barred, no-punches-pulled posthumanity. Most of humanity's descendants here are polises of minds running as software on immense architectures, speeding, slowing, inverting, amending, cloning, and re-merging one's own mind, and Egan rigorously pushes ideas to extremes that few authors are willing to extend, these are not humans in chrome bodies, they have a gender angle, they fork copies, they treat mathematics as the fictitious discovery of new mathematical landscapes. I found the substituted pronouns (vis for his, ve for he) particularly annoying and jarring, and I had to constantly flick to the glossary to try and extract some meaning from the narrative because the overwhelming number of new terms and ideas made this book challenging. The plot kicks off after an unanticipated, unexplained gamma-ray burst irradiates Earth, and these minds resolve to explain the phenomenon and find a way of protecting humanity from it in the future, which carries them, eventually, through various solar systems, and eventually across universes into another Universe with different physical laws. This is more a collection of short stories with a (rather tenuous) common thread, this ill-matched heap of far-out stories and essays mascarading as a novel, and in whole stretches you feel you've wandered into a college lecture on theoretical physics. My advice: just let the physics stuff fade out like white noise and don't worry if you didn't "get" exactly what was being described, skip or skim the long science rants, and know that even when I was completely lost it was easy to continue forward and keep reading without suffering for it. The cost of the rigor is warmth, so much intelligence, but so little to get a hold of emotionally, the characters hardly have emotions, don't seem to react much to one another, and Yatima especially is semi-human with demi-feelings and only a reader-extrapolated depth. And the ending?? it is a fairly anti-climatic ending that didn't seem to do justice to the journey preceding, one that leaves the reader (or at least this reader) thinking, huh. All this epic stuff, and it all just fizzles out. Still. If you want an exploration of what it might mean to be human, if the "pointless, arbitrary restrictions" of the ordinary human condition were loosened or removed, where the science is an essential component of the story that it tells, Egan is one of the finest and most important writers working in SF today. As always with Egan, load up on brain accelerant before reading.