Nebula Best Novel winner (2001).

Kamoj Argali is the young ruler of an impoverished province on a backward planet. To keep her people from starving, she has agreed to marry Jax Ironbridge, the boorish and brutal ruler of a prosperous province. But before Argali and Ironbridge are wed, a mysterious stranger from a distant planet sweeps in and forces Kamoj into marriage, throwing her world into utter chaos.