Trade of Queens: Book Six of the Merchant Princes, The

Charles Stross

A dissident faction of the Clan, the alternate universe group of families that has traded covertly with our world for a century or more, have carried nuclear devices between the worlds and exploded them in Washington, DC, killing the President of the United States. Now they will exterminate the rest of the Clan and keep Miriam alive only long enough to bear her child, the heir to the throne of their land in the Gruinmarkt world.