Mme de Staël and Benjamin Constant remain two of the most significant and beguiling thinkers produced by the revolutionary age. Yet until now, no full-length account has been written about their notorious affair, and it is this gap that Renee Winegarten sets out to fill. She has every reason to do so. The liaison dominated Constant’s and Mme de Staël’s lives for 17 years between 1794 and 1811. It exercised a major influence on their thought and writings, and encompassed an impressive walk-on cast including Napoleon, Talleyrand, Goethe and Byron. Its story illuminates the history of Europe at one of its most important and dramatic junctures.

The book begins slowly, not helped by frequent chronological shifts of gear. It makes some sense to begin with the first meeting between Constant and Mme de Staël, in Switzerland on September 18 1794, but this necessitates some confusing flashbacks to fill in the protagonists’ early lives during the complex period of the French Revolution. It also grates that the protagonists, who are known to posterity by their surnames, are referred to throughout as Germaine and Benjamin, like characters in a romantic ­novel. But the book soon gets into its stride, helped by the fact that the story it tells is so extraordinary, culminating in Mme de Staël’s years as a one-­woman opposition to Napoleon, her exile from Paris, her triumphant return at the dictator’s fall, and her early death in 1817.

Of the pair, Mme de Staël has always been the better known. Her novels Delphine and Corinne helped found the Romantic movement, while her non-fictional De l’Allemagne introduced contemporary German literature and philosophy to the rest of Europe. The prodigiously talented daughter of Louis XVI’s celebrated finance minister, Jacques Necker, all her life she remained a champion of constitutional government and political liberty.