A multi-faceted space opera detective story. It's detailed and pretty exciting, but a lot of characters are introduced in the first 20 pages or so, and it's a little hard to keep track of who's who when you don't know who are going to be the important ones (clue: they all are).
The habitats of the Glitter Band (satellites around planet Yellowstone) are part of a libertarian demarchy (democratic anarchy), which means constant polls of everyone about everything. Paonoply is the organisation in charge of the polling cores in each habitat and general policing. Within that framework, each habitat can apply whatever system its citizens sign up for, including obscenely vile "voluntary tyrannies", hippy-esque idylls and others where everyone is in PVS or other forms of abstraction or virtual reality.
The story opens after a habitat (and nearly 1000 inhabitants) has been blown up, apparently in a dispute over the purchase of an artwork. It turns out that far more powerful forces are at work. Tom Dreyfus is the Panoply prefect in charge of investigating the case. Meanwhile, one of his deputies, Thalia Ng, visits four other habitats to install trial polling software upgrades. Their stories diverge for much of the book, which gives it breadth, even though you know there will be plenty of overlap between the two.
As befits the writing of a "proper" physicist, the future science is (mostly) plausible, but Reynolds doesn't fall into the trap of explaining too much at a time (which would be artificial and disrupt the story). In fact often things are mentioned and the reader is left wondering what on earth it is until there is the first hint of explanation several chapters later. It all adds to the suspense.
I have only minor criticisms plot-wise. Very early on, one of the prefects seems to have another agenda. I would have preferred it if that plotline had come later, or been vaguer in the early stages. The other niggles concern the end of Thalia's time on the last habitat she visits and the qualifications (and disqualifications) for being Supreme Prefect - rather too far-fetched for my liking.
Many different types of being/consciousness fill the pages, but whilst hints are dropped about racism against hyperpigs by baseline humans, the main themes of the book are much bigger: freedom, democracy and power; consciousness (of "live" beings, machines and hybrids thereof); the old quandary of whether the ends justify the means (whether a benevolent tyranny is better than anarchistic collapse, whether the police should be armed (you can tell he’s a British writer!)); machines going rogue, and whether revenge and justice can ever be the same thing. Fortunately, he lets the reader decide on these issues; there are plenty of shades of grey. For example, there is a degree of understanding for those that could easily be labelled bad, one time explicitly saying such a character is not "a bad man" but "a man who believes bad things".
If you prefer moral absolutes, or you’re particularly fond of clocks and clockmakers, this is probably not the book for you!