This complex, ambitious novel of Renaissance Italy by the author by Byzantium explores volatile events of the period from 1491 to 1508, as dukes of Naples and Milan scheme viciously, the Pope and the Holy Roman Emperor play politics and the runty Valois king Charles VIII claims kinship with the house of Milan in order to "crusade" over the Alps and install French authority. The tale's appealing protagonist is Beatrice d'Este, who cherishes the poetry of Dante and maintains a healthy awe for the goddess Fortune. Wedded at 15 to faithless, dark-haired Lodovico Sforza, 40, the cruelly powerful son of an upstart condottiere, Beatrice first loathes and then loves her callous spouse, though the development of their relationship is not convincing. Throughout, Beatrice vies with shrewish cousin Isabella of Aragon for the title of Duchess of Milan. Scenes of torture, sex and childbirth; texts of letters; descriptions of gowns, artifacts, dreams, ceremonies and hunt parties; and inserted passages of explanatory history (Leonardo da Vinci periodically reports as engineer at the court of Milan) add color and texture. The narrative sometimes sags beneath the weight of its supernumary characters and compulsive documentation, but the play of strongwilled personalities against a vivid historical background produces a satisfying tale.