Compared to the previous entries to the "Quiet War" series, this novel was something of a disappointment, definitely nowhere near as good as McAuley's other work.
It's nominally set in the same universe as the the Quiet War series, but about a thousand years in the future. While it continues the story of one of the characters from those books (which makes it hard to understand for those who haven't read them), it's otherwise a self-contained story. It's set in a solar system where the posthuman "Quick" have been enslaved by old-school "True" humans, while the Ghosts from the Quiet War series make a reappearance.
There are three storylines: one follows a mysterious child from (apparently) the time of Greater Brazil, one follows Isak, a "True" investigator who protects a data library from age-old viruses, and Ori, a Quick slave who gets caught up in the larger conflict for the system. None of these plotlines really works, and they come together for a rather confusing and underwhelming conclusion. A lot of the worldbuilding is equally confusing, making the whole thing rather hard to follow. In particular, it's never really made clear how Isak's "exorcisms" of computer systems work- they seem to take part in a matrix-esque simulation, but quite how it works, as with much of the detail of this world, is never explained.
One final quib I have is the rather frustrating lack of information as to what happened to the solar system's civilisation after the Quiet War- there are a few vague mentions of it, but they are, like so much else, never properly explained, and it would probably have been more satisfying were this an entirely standalone novel.
In short, this novel is nowhere near as good as the excellent first two novels of the Quiet War series.