This is Reynolds’ second novel, and it’s set in the same universe as Revelation Space, but it’s not a sequel. It’s a stand-alone story, but it fills in a lot of the background to the earlier book. At first, it seems like it’s going to be a simpler story - we don’t have the intertwining multiple viewpoints going on this time - but as the book progresses, it turns out to be a great deal less simple.
Tanner Mirabel, formerly a soldier, more recently a security specialist on Sky’s Edge[1] is pursuing Argent Reivich, who he holds responsible for the death of his employer’s wife. He takes passage on a ship to Yellowstone, home of the famous Chasm City. But when he awakes from “reefersleep” he has some unexpected problems. For a start, he’s lost a lot of his memory. Then he learns that the once glorious Chasm City has been devastated by the Melding Plague, a nanotechnological virus that turns high-tech machines - including the implants that most people had in their brains - into twisted, distorted and often deadly forms. The city is now divided in two - at the lower levels there’s the Mulch, a dark damp dystopia more than slightly reminiscent of Blade Runner, while high above in the Canopy live the rich, most of whom are effectively immortal.
Having been apparently infected with a tailored virus before leaving Sky’s Edge, Mirabel starts having dreams about Sky Haussman, who was killed three centuries earlier after a terrible crime. But as the dreams turn into flashes of memory, Mirabel begins to wonder if there is something else in his past…
As is generally the case with Reynolds, there’s a good selection of supporting characters, a lot of misdirection and confusion, with everything coming together in an unexpected way. Before the story ends, Mirabel learns the truth about his own background, the origins of Chasm City, the cause of the Melding Plague, and much more. And at the end, having learned more than he could ever have expected, he starts work on changing Chasm City for the better.
He seems to have been inspired by an interesting thought:
How long would you have to live; how much good would you need to do, to compensate for one act of pure evil you’d committed as a younger man?
This being a Reynolds novel, there’s much more going on than I’ve mentioned here. If you’ve read Revelation Space, you’ll get a lot out of this - some things that were only alluded to in the earlier book are explained here. But it works well enough on its own, and I’m happy to recommend it to anyone who likes their sf hard and their plots convoluted.
[1] Which was where Ana Khouri came from in Revelation Space
. I managed the usual 10km in a little under 20 minutes, with a peak heart rate of 138. After just over a month of being mostly inactive, it was hard work, but not too hard. 
