Anne Perry 
Tathea 

Exiled from her palace by a bloody coup, an empress travels the dangerous wilds of her kingdom in search of enlightenmentand righteous vengeance The empress Tathea is awakened by the sounds of insurrection. The army, the aristocracy, and the royal guard have all turned against her husband, and stained the palace with his blood. Were she an ordinary ruler, she might follow him to the grave, but Tathea is a child of the wild lands. She comes from the desert, so to the desert she flees. Across the kingdom she travels, searching for shelter, friendship, and an explanation for the tragedy that destroyed her old life. As she fights to stay alive, she finds a book whose message might tip the scales in the battle between good and evil, changing the world forever. If her life is to have meaning, Tathea will have to spread the word. Tathea is the first book in the Tathea series, but you may enjoy reading the series in any order.