Barrès, Paul Bourget were leading authors of the period who employed fiction as a convenient vehicle for ideas about men and things. The tradition of the Balzac and Zola inspired roman-fleuve continued to exert a profound attraction, as in Romain Rolland's Jean-Christophe (1906–1912). Paul Léautaud (1872-1956) was the author of a highly original personal diary chronicling the life of the Parisian literary world in the first half of the 20th century in his monumental 13-volume "Journal Littéraire", considered to be "the greatest study of character ever written" by Mavis Gallant, and "more devastating in its truthfulness than the Confessions of Rousseau" by his biographer Dr James Harding. Popular fiction and genre fiction at the start of the 20th century also included detective fiction, like the mysteries of the author and journalist Gaston Leroux who is credited with the first "locked-room puzzle" -- The Mystery of the Yellow Room, featuring the amateur detective Joseph Rouletabille (1908) -- and the immensely popular The Phantom of the Opera (1910). Maurice Leblanc also rose to prominence with the adventures of gentleman-thief Arsene Lupin, who has gained a popularity akin to Sherlock Holmes in the Anglophone world. From 1914 to 1945 Dada and Surrealism The First World War generated even more radical tendencies. The Dada movement—which began in a café in Switzerland in 1916—came to Paris in 1920, but by 1924 the writers around Paul Éluard, André Breton, Louis Aragon and Robert Desnos—heavily influenced by Sigmund Freud's notion of the unconscious—had modified dada provocation into Surrealism. In writing and in the visual arts, and by using automatic writing, creative games (like the cadavre exquis) and altered states (through alcohol and narcotics), the surrealists tried to reveal the workings of the unconscious mind. The group championed previous writers they saw as radical (Arthur Rimbaud, the Comte de Lautréamont, Baudelaire, Raymond Roussel) and promoted an anti-bourgeois philosophy (particularly with regards to sex and politics) which would later lead most of them to join the communist party. Other writers associated with surrealism include: Jean Cocteau, René Crevel, Jacques Prévert, Jules Supervielle, Benjamin Péret, Philippe Soupault, Pierre Reverdy, Antonin Artaud (who revolutionized theater), Henri Michaux and René Char. The surrealist movement would continue to be a major force in experimental writing and the international art world until the Second World War. The surrealists technique was particularly well suited for poetry and theater, although Breton, Aragon and Cocteau wrote longer