The autobiography of a man who became pope by accident at the age of fifty-three after a youth of poetry, illegitimate children, diplomacy, and conversion. Pius II wrote the Commentaries in the late 1450s and early 1460s as a defence of his pontificate; the prose is direct, sharp, and unusually personal for a fifteenth-century memoir.
The chapters on his return to Corsignano and his decision to rebuild it as Pienza are the best window onto how the city you visit today came into being. The two-volume Harvard I Tatti Renaissance Library edition has the Latin facing the English translation.