Another thread tells, in flashbacks, of Tanner's association with the arms dealer Cahuella back on Sky's Edge, and Cahuella's wife Gitta (with whom he falls in love), and Reivich's attempt on Cahuella's life (in revenge for Cahuella supplying the weapons that killed Reivich's family), which led to Gitta's death. Finally, Tanner has apparently been infected with an "indoctrination virus," which implants memories of Sky Haussmann, the sometimes revered, sometimes hated, last Captain of the first ship to reach Sky's Edge. As those memories return to Tanner, at first in dreams, later more insistently, he learns a somewhat different, much stranger, story of the journey of the colonizing generation starships from Earth to 61 Cygni.

As the reader expects, these threads converge, leading to revelations about Tanner's past, the truth about Sky Haussmann, the real nature of the Yellowstone colony, the place of humans in the universe, and the emptiness of the revenge motive. To a pretty impressive extent, Reynolds manages to deliver on some of the rather large implicit promises he has made the reader: for one, these threads dovetail pretty well; for another, some of the big revelations are pretty neat. On the other hand, the whole revenge motif seems forced from the beginning, and the resolution to that aspect, while twisty enough to be interesting, doesn't quite convince.

This is a better novel than its predecessor, though not without faults. First the good stuff: it's full of neat SFnal ideas, not necessarily brilliantly new, but very well-realized: the generation ships (treated rather differently than usual in SF), some genetic technology, some alien ecosystem stuff, even a hint of a communication system reminiscent of the Dirac Communicator in James Blish's "Beep." It sets up expectations for a pretty spectacular closing revelation, tying together the three threads, and as I've said, it pretty much delivers on those expectations. The resolution had elements that I expected, and which were nicely foreshadowed, plus elements that were a great surprise, but which still worked for me. Thus, I'd say, that in terms of large-scale plot and setting, the book works very well. As for the prose, it's sound, serviceable, hard SF prose: nothing impressive, but not too clunky either. The faults, then, lie in some small-scale plot elements, and characterization.

The plot, particularly Tanner's attempts to find Reivich, depends on a lot of implausible coincidence and luck, super-powerful characters who still don't kill their rivals when reasonably they should, and secret organizations suddenly being penetrated by little more than brandishing a gun in the face of underlings. More tellingly, the characters are a bit under-motivated, and they are pretty much all evil and violent, but not really presented in such a way. More than several times, we are told that such and such a character, single-mindedly bent on killing several other characters, is really not bad and is justified in so doing. This seems to represent an awfully cynical view of humanity: everyone is purely out for number one, and is pretty much ready to kill anyone in their way.

On balance, this is a pretty impressive book. The faults are the faults of much SF, especially hard SF, and the virtues are the virtues of the same sort of SF. It doesn't, then, transcend its sub-genre at all, although it does do very well within those boundaries. And for a long book, it reads smoothly enough, and keeps the interest. In this way it is an improvement on the slightly shorter Revelation Space, which seemed significantly too long. While I wouldn't say that Chasm City might not benefit from some judicious cutting, it fills its page count reasonably well. It's another step towards what could become a very significant 21st century hard SF career.