Ace Books, 2008, 336 pages
In Saturn's Children, Freya is an obsolete android concubine in a society where humans haven't existed for hundreds of years. A rigid caste system keeps the Aristos, a vindictive group of humanoids, well in control of the lower, slave-chipped classes. So when Freya offends one particularly nasty Aristo, she's forced to take a dangerous courier job off-planet.
The cover and the story makes a lot more sense if you know your Heinlein.
Also by Charles Stross: My review of Accelerando.
My complete list of book reviews.