The inimitable Nancy Mitford's account of Voltaire's sixteen-year affair with the comely Marquise du Châtelet—in her own right a renowned mathematician and original expositor of Newtonian ideas—is a spirited romp in the company of two extraordinary individuals as well as an erudite and gossipy guide to French high society during the Enlightenment.<br>  <br> The lusty and algebra-obsessed marquise, it so happens, was also in love with another mathematician, Maupertuis, and devoted to gambling besides. She had a rival for Voltaire's affections in the future Frederick the Great of Prussia, and later in the scampish philosophe's own niece. There was, at least, no jealous husband to contend with; the Marquis du Châtelet, the author assures us, always behaved perfectly. It was in fact the couple's Parisian contemporaries who reacted the worst, not so much with sexual jealously as at the thought of their brilliant conversation wasted on the windswept hills of Champagne, site of the Château de Cirey, where the lovers, equipped with experimental laboratories, a darkroom, and an immense library of more than twenty-one thousand volumes, pursued their <i>amours philosophiques</i>. Not infrequently word of an impending arrest would send the great gadfly Voltaire scurrying across the border into Holland. Nevertheless, thanks to his irrepressible charm—and the interventions of powerful friends—he would always find his way back into the marquise's arms, and into another chapter of this supremely entertaining popular biography.