Which C.S. Lewis novel follows the space travels of philologist Elwin Ransom?

Out of the Silent Planet follows the space travels of the philologist Elwin Ransom. C.S. Lewis published the novel in 1938 as the first volume of his Space Trilogy.

Ransom is kidnapped and taken to Malacandra, the planet humans call Mars. There he encounters intelligent species and learns that Earth is regarded as a fallen or “silent” world within a wider cosmic order.

The novel combines planetary adventure with theological and philosophical ideas. Lewis wrote it partly in response to what he saw as the limitations of some modern space fiction, especially stories treating other worlds as settings for conquest alone.

The later books, Perelandra and That Hideous Strength, continue Ransom's story but shift from interplanetary exploration toward spiritual conflict and a threatened society. The series is also called the Cosmic Trilogy or Ransom Trilogy.