A human astronaut lands on a distant planet only to discover a society where primates hold dominion over a primitive, feral human population. Ulysse Mérou, a journalist, joins a space expedition that reaches the star system of Betelgeuse, where he finds a world governed by an advanced civilization of apes. As he attempts to prove his own intelligence to his captors, he faces the physical constraints of a society that views humans as mere animals. The narrative framework utilizes a frame story, beginning with a manuscript found in space, which introduces the reader to Ulysse's harrowing account of his survival and eventual escape.

Readers and critics frequently note the sharp, satirical edge Boulle employs to dismantle human exceptionalism. Discussion often centers on the unsettling nature of the role reversal between humans and apes, which forces a re-evaluation of how humanity treats other species. The pacing is described as brisk and efficient, prioritizing the philosophical implications of the premise over intricate world-building details. Many observers highlight the ending as a significant point of debate, as it provides a cynical conclusion that lingers long after the final page. The work remains a foundational text for those interested in speculative fiction that functions primarily as a mirror for contemporary societal flaws.