[1][2] An E-book edition was published by Gollancz's SF Gateway imprint on September 29, 2011 as part of a general release of de Camp's works in electronic form.

The truth of their origin has faded into legend, and as a result the story of the space voyage and the scientific theory of evolution have become competing accounts of the genesis of humanity.

Marko Prokopiu, a schoolteacher in Skudra the conservative country of Vizantia, has been converted to Anti-Evolutionism by his houseguest, travel writer Chet Mongamri of Anglonia, and as the story opens is found guilty in court having taught the heresy to his students.

His old professor hides him from the authorities and introduces him to the Anglonian philosopher Boert Halran, who is in Vizantia to acquire sealant for his experimental hot air balloon.

The plan is to spirit Marko out of Lann on its first flight and then fly onward to Vien in Eropia, where Halran intends to present the balloon at a philosophical convention.

The Afkans are hostile to all outsiders, but are persuaded to spare their lives and release them in return for being taught how to build a super weapon (a ballista) to help defend their island.

Marko and Halran resume their flight, only to be again forced down on Mnaenn, the island of women, where an all-female society of witches adhering to the cult of Einstein jealously guards the Great Fetish, said to hold the truth regarding human origins.

In addition to Halran's balloon, the latest wonders are the discoveries in optics by Dama and Ryoske Chimei, two brothers from Mingkwo who have invented a telescope and microscope.

The names of other countries and locales are also corruptions of earthly originals, including Eropia (Europe), Afka (Africa), Lann (London), Niok (New York), and Vien (Vienna).

De Camp previously wrote about the actual struggle between science and creationism in The Great Monkey Trial (1968), a non-fiction account of the 1925 test case against Tennessee's Butler Act, which made the teaching of human evolution in that state illegal.

[5] His portrayal of the parental permissiveness and juvenile delinquency that disturb Marko in Lann echoes previous criticisms made in his 1957 short story "Let's Have Fun."

"[6] Publishers Weekly, while characterizing it as a "happy combination of gentle satire and light adventure," and its author as "an old pro" who "can be relied upon to entertain and amuse," felt that, notwithstanding, "in this case, he has nothing new to show us.

"[8] Mel Gilden in the Los Angeles Times thought it "an adventure with a thin overlay of science-fiction ... "lack[ing] energy and excitement [with] [t]he climactic revelation ... telegraphed from the beginning."