Which C.S. Lewis book, published in 1938, began his science-fiction trilogy?

Out of the Silent Planet, published in 1938, began C.S. Lewis’s science-fiction trilogy. The novel follows the philologist Elwin Ransom after he is abducted and taken to Malacandra, a planet that humans call Mars.

The book was Lewis’s first published work of science fiction and responded partly to what he saw as an overemphasis on materialism and aggressive colonial expansion in contemporary speculative fiction. Its extraterrestrial societies are presented through language, ethics, theology, and cultural difference rather than only through technological spectacle.

The two later novels are Perelandra, published in 1943, and That Hideous Strength, published in 1945. Together, the three books are often called the Ransom Trilogy or the Cosmic Trilogy. Perelandra takes Ransom to another world resembling an unfallen Eden, while That Hideous Strength returns the conflict to Earth and gives the trilogy a more overtly dystopian setting.