What was C.S. Lewis’s first published book of science fiction?

Out of the Silent Planet was C.S. Lewis’s first published science-fiction book.

Published in 1938, Out of the Silent Planet follows Elwin Ransom, a Cambridge philologist who is kidnapped and taken to Mars, called Malacandra in the novel. Ransom discovers that the planet contains intelligent species and a moral order very different from the assumptions of his captors.

The novel began Lewis’s Space Trilogy, followed by Perelandra in 1943 and That Hideous Strength in 1945. It is sometimes described as Christian science fiction because it engages with ideas about sin, redemption, language, and intelligent life beyond Earth. The book’s title reflects Lewis’s fictional historical belief that Earth had become spiritually isolated from the wider cosmos.