Micro review: WOW!!!
Mini Review: This novel has everything: divergent human species, uploads, nanotechnology, gamma ray bursters, traversable wormholes, picotechnology, multidimensional physics and the most bizarre aliens I have ever read about.
Diaspora is a posthuman novel from the beginning. Only one of the main characters have ever had a biological body, and the entire first chapter contains the description of how small infomorphs are made (the storks have been replaced by genetic algorithms, simulated gradients of morphogens, neural networks and hebbian learning). Most of the events occurs inside the virtual worlds running in the "polis", dense nanocomputer networks where the infomorphs ("citizens") live, although these realities are often seamless blends between physical and virtual reality (one of the main questions is whether the physical world does matter or not - some citizens prefer to withdraw from reality altogether, while others crusade for "realism").
Of course, Egan could not make the characters too alien, since one of the principal requirements of a working novel is that the reader is able to identify with the characters. So despite the fact that they rewrite parts of their minds, copy, merge, download into physical bodies or branch out in mutated copies they are pretty human in many ways. Egan consistently uses gender neutral pronoun for the infomorphs ("ve" instead of "he/she", "ver" instead of "his/her" and so on), although some of the characters still gave me a male or female impression.
What really makes Diaspora into a great novel is the magnificient imagination and scientific know-how. This is hard science fiction as it is meant to be: no rayguns or warp drives, but ten-dimensional grand unified theories, the rotational dynamics of binary neutron stars and high level particle physics instead. I must admit that I wonder how much this book does require of the reader, I found myself reviewing my notes from my old course in topology at one point and sketching diagrams of fibre bundles. Hopefully the ordinary reader can simply accept the concepts as technobabble, technobabble which turns out to be well researched and consistent. Regardless of its level, it is clear that Egan has one of the most fertile imaginations around, rivalled only by Iain Banks and David Zindell. Unlike them, he really manages to show how the miracles are done, often in surpising detail.
As a whole Diaspora is a grandiose zoom outwards, from the bits in a nanocomputer hidden under the siberian tundra to ever more cosmic scales. When the reader has got used to one miracle Egan zooms out again, and the previously titanic suddenly looks rather commonplace. The tension lies not as much in the plot as in the question: "how will Egan outdo this"? And Egan does really succeed. The final monument to the creativity of intelligent life and the infinite possibilities of physics is truly impressive, and points towards even more grandiose possibilities.