Neptune's Brood — Charles Stross

The year is AD 7000. The human species is extinct--for the fourth time--due to its fragile nature.

Krina Alizond-114 is metahuman, descended from the robots that once served humanity. She's on a journey to the water-world of Shin-Tethys to find her sister Ana. But her trip is interrupted when pirates capture her ship. Their leader, the enigmatic Count Rudi, suspects that there's more to Krina's search than meets the eye.

He's correct: Krina and Ana each possess half of the fabled Atlantis Carnet, a lost financial instrument of unbelievable value--capable of bringing down entire civilizations. Krina doesn't know that Count Rudi suspects her motives, so she accepts his offer to get her to Shin-Tethys in exchange for an introduction to Ana.

And what neither of them suspects is that a ruthless body-double assassin has stalked Krina across the galaxy, ready to take the Carnet once it is whole--and leave no witnesses alive to tell the tale...