Which C.S. Lewis novel begins the Ransom Trilogy?

Out of the Silent Planet begins C.S. Lewis's Ransom Trilogy.

Published in 1938, the novel introduces Elwin Ransom, a Cambridge philologist who is kidnapped and taken to Mars, called Malacandra by its inhabitants. The story combines planetary adventure with philosophical and theological ideas about humanity, language, and civilization.

The second book is Perelandra, published in 1943, and the third is That Hideous Strength, published in 1945. Although the three novels share Ransom and a wider cosmic conflict, their settings and narrative styles differ considerably.

The trilogy is sometimes called the Space Trilogy. That name is useful, but “Ransom Trilogy” emphasizes the central character. Lewis drew on his interest in medieval cosmology and science fiction, while his friendship with J.R.R. Tolkien helped sustain his enthusiasm for imaginative literature.