What is the theme in The Hero and the Crown by Robin McKinley?

Courage is a major theme in the story. The novel is set in a time when knights fought in chain mail and kings were men of honor. Chivalry was a way of life. Aerin, however, is a female child; therefore, her role is that of a lady, someone who decorates a room with her beauty and her silence. Aerin is not happy with this role. Aerin wants to learn to wield a sword, to fight alongside the men. Aerin wants to be more than the child of the king's second wife, a woman rumored to have been a witch.