There's nothing like a good alien invasion story, unless it's a good alien invasion story with an unusual twist. And that's what Nat Schachner and Arthur Leo Zagat gave the readers of Amazing Stories magazine when they picked up the April 1931 issue and read the cover story, "The Menace from Andromeda".
Space aliens invading the Earth was already a well-established science fiction trope when Schachner and Zagat wrote their story in 1930. The subgenre was established, as so many were, by H. G. Wells. The War of the Worlds, first serialized in 1897, set a pattern of alien invasions that was followed by G. McLeod Winson's Station X (1919), Edgar Rice Burroughs' The Moon Men (1925), Edmond Hamilton's "The Other Side of the Moon" (1929), and Harl Vincent's "The War of the Planets" (1929).
Schachner and Zagat gave the familiar story a twist, by replacing the invading alien race with Alcoreth, a single creature traveling through space as a cloud of spores, in a fictionalized version of Svante Arrhenius' panspermia hypothesis. Alcoreth was not looking to conquer the Earth so much as colonize it; and the most menacing aspect of the Menace from Andromeda was Alcoreth's complete indifference to the existence of humanity. As a collective being, Alcoreth may not even have been aware of the concept of individual life forms. The second section of the story is told from Alcoreth's point of view, and this is the story's most sustained bit of invention. Sadly, Schachner and Zagat never return the story to Alcoreth, so we never learn how she sees the new world she has settled on.
As my friend David Mix Barrington has noted in comments, Schachner and Zagat's view of the world nine years in their own future is considerably more advanced than the reality turned out to be. In their 1939, Columbia University has relocated to a 100-story skyscraper in Central Park, and New York City has a new City Hall Tower of 150 stories. Civil aviation is also more advanced, as Donald Standish owns a twin-engine aircraft that can apparently travel across North America without refueling. Finally, the various wars that plagued the real 1930s are absent from Schachner and Zagat's version. I think Schachner and Zagat, writing in 1930, expected the economic crisis of the time to right itself in fairly short order, which was what pretty much everyone from President Hoover on down expected to happen.
The President of the United States in 1939 was not a third Adams, but was a second Roosevelt, which counts as a near miss. In the story, the head of the U.S. Army (the actual title is Chief of Staff of the United States Army) in August 1939 was named General Black; in reality, it was General Malin Craig, like the fictional Black a grizzled veteran of World War I. On September 1, Craig was replaced by General George C. Marshall.
In the story, Alcoreth is finally defeated when Douglas Cameron infects her with cancer, in an echo of the defeat of Wells' Martians. This may count as one of the earliest descriptions of bacteriological warfare.
To a modern reader, one of the most appalling things in the story is the offhand treatment of Mary Cameron. After the trio return to Douglas Cameron's laboratory in Colorado, the two men send her off to bed after promising her that they'll bring her up to speed on their deliberations after she wakes up. They do no such thing. In fact, not only do they break their promise to Mary, they take off in Standish's plane while she's still asleep, leaving her completely in the dark about what's going on. One can imagine her waking to the sound of Standish's twin-engine plane taxiing out of the hanger, and rushing outside just in time to see it take off, cursing her faithless brother and fiance as it vanishes into the east. After that, it would take a greater miracle than the defeat of Alcoreth for Standish to convince Mary to go ahead with the marriage.