by Charles Stross
Ace, 2003, ISBN 0-441-01072-5
A book review by Elisabeth Carey
The Singularity happened in the mid-21st century, and the Eschaton was born. It quickly departed from Earth, but before leaving it dispersed much of Earth's human population to other habitable planets--with some of those involuntary colonies moved centuries into the past, and some better-equipped than others to maintain a technologically advanced civilization. A few centuries later, Earth and the various colonies are still rediscovering each other, and still working out the rules for getting along (or not.)
One absolutely inviolable rule is that Thou Shalt Not Tamper With Causality. This is not because of any great moral commitment to Not Cheating, or even a reflection of a general recognition of the potential for disaster in tampering with their own history, but because the Eschaton--committed above all to the protection of its own existence and the historical conditions which created it--severely punishes any entities that commit such violations. By "severely," I mean they eliminate the entire inhabited system where such violations occur.
Singularity Sky opens with the invasion of a borderline-interstellar civilization of politically backward tendencies (the thriving economy of Warsaw Pact Europe, the forward-looking social policies of Czarist Russia) by the Festival, a collection of uploaded minds no longer bearing much resemblance to human beings who travel around trading information for information, wreaking social, political, and economic devastation everywhere they go. The New Republic (which is what this very backward monarchy calls itself) demonstrates its clear-headed grasp of the situation by attempting make war on the Festival. In order to get its military forces into the only position in which they'll have a chance of doing much good (in the Rochard's World system just before the arrival of the Festival) they decide to commit a tiny, unimportant little causality violation that the Eschaton won't notice.
Fortunately, Rachel Mansour and Martin Springfield are already in the New Republic. Rachel's an agent of the UN, a trouble-shooter who specializes in preventing mushroom clouds and other unpleasantnesses. Martin's an agent of something else, with a mission that isn't quite as clear, but his immediate assignment, or cover, is making sure the engines on the New Republic Navy's shiny new flagship are function correctly. They each find their way onto the ship as it heads out on its mission of defense and causality violation. Dodging secret police and outraged naval officers, and not quite trusting each other yet, they find themselves working together in an attempt to survive long enough to minimize the disaster about to overtake the guys who are trying to kill them.
And I haven't even mentioned the revolting peasants, the socialist revolutionaries, or the family ties of the secret policeman assigned to get the goods on Martin.
This is a light, fast-paced, entertaining read, well worth an evening or two.