While the marquis de Sade was drafting The 120 Days of Sodom in the Bastille, another libertine marquis in a nearby cell was also writing a novel—one equally outrageous, full of sex and slander, and more revealing for what it had to say about the conditions of writers and writing itself. Yet Sade's neighbor, the marquis de Pelleport, is almost completely unknown today, and his novel, Les Bohémiens , has nearly vanished. Only a half dozen copies are available in...