I picked up a copy of the revised edition of the SF Handbook by the de Camps, and I found his take on the late 30′s boom in SF publishing interesting.
Sprague lays the blame at the feet of Orson Welles’ War of the Worlds radio play.
He notes that the boom began in the autumn of 1938, that there were four magazines on the stands at the time (Amazing, Astounding, Thrilling Wonder and Weird Tales) and a fifth – Marvel Tales – was being launched.
He then says “But it was an event unrelated to publising that gave the greatest momentum to speculative fiction. At 8:00 p.m., on the evening of October 30, 1938, the twenty-three-year-old orson Welles staged the first radio broadcast of H. G. Wells’s 1898 story, The War of the Worlds.”
…”For science fiction, however, the event was a turning point. Many who had never read Wells’s stories hunted them up. Others bought copies of those magazines with the bug-eyed monster covers….Soon, seven more science fiction magazines were launched. On July 2, 1939, the First World Science Fiction Convention met at Caravan Hall on East 59th Street, New York City. Two hundred fans gathered from all over the United States and Canada….Time wrote up the convention…Harper’s…took a sharp and not friendly look at the phenomenon….Despite this blast, science fiction continued to expand.”
He notes that a similar expansion followed the end of WWII, much like detective fiction enjoyed a surge following WWI.
My own experience tells me that another ‘boom’ occurred in and around the excitement of the space program’s moon shot (including the Mercury and Gemini programs leading up to Apollo).
It makes a good case for the contention that the genre has only enjoyed expansion through the influence of events external to the genre, and it makes me wonder why, in times past when such things occurred, they led to an increase in both the production and consumption of literature and now, they lead to the increased production and consumption of any form that isn’t literature.