Five Twelfths of Heaven - Book One of The Roads of Heaven - Melissa Scott

In a space-faring civilization where a single woman is increasingly sisenfranchised, the star pilot Silence Leigh is defrauded from her inheritance by a greedy competitor. Forced to ally with two men, Silence is dragged into a deadly political struggle, and is tantalized by the hints of the legendary Earth, as well as the dread and the glory of Magi's power. Her dreams of having her own ship and of escape from the Hegemony's oppressions take on new direction and focus when she joins the crew of "The Sun-Treader"

"Polyamourous alchemical space-opera..." - Jo Walton