Bartolomeo Platina (1421-1481), historian, political theorist, and author of a best-selling cookbook, began life as a mercenary soldier and ended it as the head of the Vatican Library. A papal official under the humanist Pope Pius II, he was a member of the humanist academies of Cardinal Bessarion and Pomponio Leto, and was twice imprisoned for conspiring against Pope Paul II. Returning to favor under Pope Sixtus IV, he composed his most famous work, a biographical compendium of the Roman popes from St. Peter down to his own time. The work critically synthesized a wide range of sources and...