Trawling through a vast family archive and arcane sources in half a dozen languages, Adam Zamoyski has revealed the dramatic life of his great-great-great grandmother, an uneducated, vulnerable girl cast into a man's world. Her aristocratic position enmeshed her in high politics and close encounters with Frederick the Great, Benjamin Franklin, Rousseau, Joseph II, Marie-Antoinette and Tsar Alexander I, and earned her the...