Number two in the Revelation Space trilogy; you could read it as a standalone story, but it's better to read in sequence, and it helps if you've also read Chasm City.
This is a long treasure hunt for super weapons, conducted by two competing factions (though both have the same intention), with a life-or-death deadline. Although that is true, it does it an injustice because there is far more complexity and intrigue than that implies. Reynolds has really thought out his technology, worlds, people and how they interact and evolve over very long time periods.
In fact, deceit and integrity are the main themes, with many characters living a lie (or several) and double-dealing, though it is never confusing.
The context is a power struggle amongst the Conjoiners (also known as Spiders), who are winning a war against the Demarchists (democratic anarchy), while The Inhibitors are trying to destroy intelligent life once it embarks on interplanetary travel. This creates plenty of threads to the story, keeps it exciting and prevents it being a simple, butch shoot 'em up or war story.
The ending (always tricky in the middle of a series) is particularly good balance: semi-satisfying if you have to wait a while before reading the final installment, but tantaliseing enough to make you keen to read on.
* The practicality of a hive mind. The Conjoiners are a human group who have developed the ability to link minds, but also, and crucially, to limit it to some extent. There are some wonderful dscriptions: "Skade peered into his mind, glimpsing a surface slurry of recent experiences and emotions... Beneath the slurry were deeper layers of memory, mnemonic structures plunging down into opaque darkeness like great drowned monuments... Down at the very deepest level, Skade detected a few partitioned private memories... she was tempted to reach in and edit the man's own blockades... Skade resisted; it was enough to know that she could." And it affects emotions too, "He felt Skade's irritation bleeding into his own emotional state." When shutting it out/off, "he felt the million background thoughts of the Mother Nest drop from his mind like a single dying sigh".
* Accelerated neural processing, which means someone could "watch an apple fall from a table and compose a commemorative haiku before it reached the ground."
* Space wars are fundamentally different from those on Earth: "no element of surprise. But there almost never was in a space war... war in space was a game of total transparency. It was a war between enemies who could safely each assume the other to be omniscient."
* Issues of extreme longevity. If you live for hundreds of years, should marriage be for life? Should youthful crimes taint later life or is it right to declare "There is no need for us to be puppets of our past"?
* "In zero gravity, heads did not loll lifelessly... in space the dead were often difficult to tell from the living."
* "The growths [melding plague, on a ship] had a mad artistry about them, a foul flamboyance which both awed and revolted... There were places where some major structure had been echoed and re-echoed in a fractal diminuendo, vanishing down to the limit of vision."
* "For the galaxy, as much as it was a machine for making metals, and thereby complex chemistry, and thereby life, could also be seen as a machine for making wars."
* "I need to have a word - a serious word - with weapon 17." (I like that because it echoes the wonderful film, "Dark Star".)
* "The symbols and sinuous indentations of the programming language resembling the intricately formalized stanzas of some [Vogon?] poetry."
Inevitably, there are irritations, but they are minor, especially when you consider the length of the book.
* There are a couple of sections where there is too much backstory in too short a time, in too unsububtle a way.
* There is plenty of detail about all the many characters and yet most of them still lack personality. For example, although there are strong and significant female characters, they could be men, if it weren't for their names and the use of her/she.
* In other books, I had wondered at how little mention there was of relationships (not that I want gory or slushy details in sci fi). This book demonstrates that Reynolds is best avoiding them. Antoinette and Xave's love scenes are awful and the sexual tension between a couple of other characters is just banal.
* Characters make Biblical analogies (the Promised Land, the Lamb, the prodigal son), though I'd be surprised if they would be understood so far away in time and space.
* There is an implausible reliance on paper documents and pneumatic tubes on Resurgam, even allowing for the fact it is a relatively poor and backward planet. Similarly, a doubt about paternity in as more advanced community could be easily solved (even with current technology).
* Too many dead people aren't really dead, or only slightly and/or temporarily so. I don't object in principle but it gets irritating when done to excess.
Overall, another riveting Reynolds. (My Revelation Space review: http://www.goodreads.com/review/show/146246012.)