The Loves of Lucrezia — Francesca Wright

The wickedest woman who ever loved. Sensual... corrupt... that was the court of Renaissance Italy, and that, too, was Lucrezia Borgia. Born into a world of unparalleled depravity, Lucrezia learned early the corrupt practices of her dissolute family. Scandalous, she was a woman of infinite guile and indiscriminate passion, whose affairs led her from page boy to prince... and to a reputation called shocking even in a land not easily shocked. Yet no matter how often she strayed, Lucrezia remained faithful - in her special fashion - to the one man she had sworn would be hers.

Novel reedited as: Lucrezia by Denise Robins.