Eschaton 3 — Charles Stross

Sometime in the twenty-third century, humanity went extinct, leaving only androids behind to fulfill humanity's dreams. And, having learned well from their long-dead masters, they've established a hierarchical society -- one with humanoid aristo rulers at the top and slave-chipped workers at the bottom, performing the lowly tasks all androids were originally created to do.               

Designed as a concubine for a species that hasn't existed for two hundred years, femmebot Freya Nakamichi-47 -- one of the last of her kind still functioning -- accepts a job from a stranger to deliver a package from mercury to Mars. Unfortunately, she's just made herself a moving target for some very powerful, very determined humanoids desperate to retrieve the package's contents…