What is the theme in Till We Have Faces by C. S. Lewis?

Death is a major theme in the book. Life is cheap in Till We Have Faces' Kingdom of Glome. Animal and occasionally human sacrifice are integral to the cult of the goddess Ungit. Premature natural death claims two queens, the second during childbirth, and the grieving King's response is to stab a wine steward to death and vow to send his slave, the Fox, to the mines, a certain death sentence. Princess Orual advises her beloved tutor to flee, but he prefers honorable suicide in the Greek manner.