Zaretsky is a historian of France and, as he admits, a newcomer to Russian history. Hence, his short and entertaining book tells readers more about Denis Diderot than about the Russian empress who invited the leading Enlightenment philosopher to St. Petersburg. When the 60-year-old Diderot arrived in Russia in 1773, it was the first time he had ventured far from home. He shared with other French philosophers of his time a view of Catherine the Great as the embodiment of enlightened despotism, a leader driven by a faith in reason and progress and dedicated to ensuring the happiness of her subjects. As the book makes clear, the philosopher initially seemed poised to realize his dream of playing mentor to the monarch. Catherine eagerly engaged in debates with Diderot. She was enthralled by his audacious thinking, and he respected her devotion to Enlightenment ideals. Mutual disenchantment was, of course, inevitable. Diderot eventually concluded that the concept of enlightened despotism was an oxymoron and that Catherine, alas, was merely a despot. Catherine, meanwhile, gradually came to see philosophers as useless, their writings paving the way to endless calamities. Sill, Zaretsky cannot help but admire Catherine and Diderot’s mutual affection, which their mutual disappointment did not diminish.