If history remembers Lucrezia Borgia at all, it is as a woman of extravagant vices whose name has become synonymous with political intrigue and poison. Cardinal Bembo is remembered primarily as the namesake of a popular typeface. But as this book of letters reveals, there was real substance, and real faces, to both of them. Borgia, a child bride who was ruthlessly exploited for political advantage by her three husbands, proved to be a girl of surprising...