Michael Saler in the Times Literary Supplement:
In 1967, Roland Barthes formally announced the death of the author, a claim that seemed to have played out from the late nineteenth century to the late twentieth. During this period, avowedly fictional characters and imaginary worlds rose to a prominence inconceivable in earlier periods, while acknowledgement of their creators’ role decreased. “Sir Arthur Conan Doyle . . . what has he to do with Sherlock Holmes?” asked T. S. Eliot. To which the Baker Street Irregulars, founded in 1934, had a ready reply: he was John Watson’s literary agent.
During the fin de siècle, imaginary places and heroes became detached from earlier religious strictures, utilitarian concerns and authorial intentions, in the spirit of art for art’s sake. Authors such as William Morris, in The Well at the World’s End (1896), started to create wholly made-up worlds with rich, internally-consistent historical and geographic backgrounds. These “secondary worlds”, as J. R. R. Tolkien called them, generated a lively tourist trade as well as outright colonialism. Adults no less than children began to inhabit them, at the level of the imagination, for prolonged periods of time, often in the company of others. This persistent and communal manner of habitation brought the world and its denizens to life beyond the control of any single author or reader. Today the collective transformation of imaginary worlds into virtual worlds occurs largely through social networks on the internet, whereas for most of the past century readers engaged in such synergistic magic through the letters pages of magazines, clubs, fanzines and conventions.
Thanks to this public conjuration, authors began to relate to their fans not as demigods but as first among equals. (For poor Conan Doyle, not even that.) Indeed, with the advent of brand-name characters appearing simultaneously in books, films, radio and advertising, the seminal role of the creator could be overlooked if not ignored completely. Authors even became fictional themselves when publishers issued their work under house names: “Ellery Queen”, the nom de plume of Frederic Dannay and Manfred Lee, did double duty as the non-existent writer of his own fabricated adventures.
More here.