Probably the best Science Fiction books I have read in years. Bear's fully imagined universe (not so, so, distant future) is simply amazing. He explains without getting lost in detail or glossing over key stuff. His New York of the future is a book in itself, never mind the complete and functional Mars he imagines. No puffy "terra forming" cop out for him, but realistic, hard scrabble living.
Key is his imagining of the future of nano technology, already being worked on in labs today, Bear puts his own spin on it. Fascinating stuff even if we are probably centuries away from the reality. Less clear are his "educational bacteria and virus" but that's ok.
The plot it not bad. It involves politics, but it is no Dune in those terms. I would guess that the political plot points are there to move the story along. The characters are all believable (even the bad guys have some dimension to them). The love life of the main folks seems a little thin, but hey, no room for everything!
One major problem I had was with the crucial plot point. Without giving too much away, to do what was done, even the first time, would in my mind create tremendous reactions on earth and mars. Neat idea but it strains credibility.
Still, a great read, lots of fun and well imagined.