Which C.S. Lewis book began his Ransom science-fiction trilogy?

Out of the Silent Planet began C.S. Lewis’s Ransom science-fiction trilogy.

Out of the Silent Planet was published in 1938 and introduced Elwin Ransom, a Cambridge philologist who is kidnapped and taken to Mars, known in the novel as Malacandra. The book combines planetary adventure with philosophical and theological speculation about language, civilization, evil, and humanity’s place in the universe.

It is the first volume of the trilogy commonly called the Space Trilogy or Ransom Trilogy. Perelandra, published in 1943, follows Ransom to Venus, while That Hideous Strength, published in 1945, returns to Earth and develops the series’ social and technological concerns.

Readers sometimes identify Perelandra as the trilogy’s starting point because it contains especially prominent theological themes, but it is the second book. Lewis wrote the trilogy partly in conversation with scientific romance traditions and with encouragement from his friend J.R.R. Tolkien, who also influenced his interest in imaginative literature.