The Revolution Business: Book Five of the Merchant Princes

Things are going badly for the Clan in this new SF novel of the Merchant Princes, the immensely popular series by Charles Stross. Locked in a vicious civil war for control over the kingdom of Niejwein, their army is bottled up inside a fortress under siege in two parallel universes at once. Duke Angbard, the Clan's leader, has been laid low by a stroke: plotters are already conspiring in readiness for the deadly dance to come.

Miriam, rescued from a tight spot in New Britain, finds the hopes of the young, progressive faction focused on her. But do they want her as a leader or a figurehead? She soon finds herself thrown into a desperate struggle for power. Meanwhile, unbeknownst to the Clan, researchers working for the US government have achieved a technological breakthrough. The War on Terror is about to go transdimensional.