Out of the Silent Planet, Perelandra and That Hideous Strength.

The Space Trilogy or Cosmic Trilogy is a series of science fiction novels by C. S. Lewis, famous for his later series The Chronicles of Narnia. A philologist named Elwin Ransom is the hero of the first two novels and an important character in the third. The trilogy was inspired and influenced by David Lindsay's A Voyage to Arcturus. According to biographer A. N. Wilson, Lewis wrote the novel after a conversation with J.R.R. Tolkien in which both men lamented the state of contemporary fiction. They agreed that Lewis would write a space-travel story, and Tolkien would write a time-travel one. Tolkien's story only exists as a fragment, published in The Lost Road and other writings (1987) edited by his son Christopher.