Genus Homo belongs to a subgenre of SF where a group of average people is suddenly thrown into a completely novel environment. Two others in this subgenre I've read in the past few years are Leinster's The Wailing Asteroid (filmed in1967 with the wildly misleadingly title The Terrornauts) and Baxter's Manifold: Origin. Genus Homo, first published in 1941 with internal references to 1939, has some connections to both. There are human / primate interactions, as in Baxter, and 1950's sexism, as in Leinster. The uncredited Richard Powers cover with humans in cages suggests The Planet of the Apes, though this edition predates that book by two years. The scene illustrated occurs -- minus the odd E=H2O formula -- but occupies just one one short chapter.

P. Schuyler Miller is pretty much forgotten today, except for old-timers who remember his monthly book review column for Astounding and Analog. L. Sprague de Camp is somewhat better remembered for novels that mixed history and SF or fantasy. That element comes into play primarily in the less-convincing second half of the novel. That may seem surprising since in the first half you have to accept that a bus full of men and women could be trapped in a collapsed tunnel for a million years, saved because one passenger was a scientist with a canister of an experimental suspended animation gas. Ironically, this passenger did not survive. But given that premise, what follows for half the book is how the group organizes and survives, with missteps along the way. Sexist, of course, but otherwise not bad for the time.

In the second half, you have to accept that the humans can learn the gorilla's language and the gorillas learn English, in what appears to be a week or two, after which point there is only difference between the two groups is governmental structure. This second half eventually moves into a major military campaign between the gorillas and baboons (or perhaps mandrills), with curious bits of lame humor.

If you have fond memories of golden-age pulp SF, you could do worse. ( )