What causes revolutions? How does public opinion influence events? This work answers these questions by asking what the French people read in the 18th century. The answer lies only partially in the canon of the great Enlightenment philosophers: Voltaire, Diderot, Montesquieu, Rousseau. More popular than these works were other books bought and sold "under the cloak". Salacious, blasphemous, often pornographic and treasonous, these formed a libertine literature that undercut all the orthodox values of the old regime. This history of these books, and of the booksellers who sold them, presents an idiosyncratic guide to the ancien regime and its citizens.