When John Hall walked on Ganymede, a thousand weird beings walked with him. He was one man on a sphere of mocking, mad creatures—one voice in a world of shrieking echoes. Sam Moskowitz was the editor Science-Fiction Plus, in addition he edited two dozen anthologies, and wrote a handful of short stories. His most enduring work is his writing on the history of science fiction, including Explorers of the Infinite and Seekers of Tomorrow, as well as the highly regarded Under the Moons of Mars: A History and Anthology of "The Scientific Romance" in the Munsey Magazines, 1912–1920.