In the final installment of Sally Christie's "tantalizing" (New York Daily News) Mistresses of Versailles trilogy, Jeanne Becu, a woman of astounding beauty but humble birth, works her way from the grimy back streets of Paris to the palace of Versailles, where the aging King Louis XV has become a jaded and bitter old philanderer. Jeanne bursts into his life and, as the Comtesse du Barry, quickly becomes his official mistress. "That...