A Voyage to Arcturus is a novel by the Scottish writer David Lindsay, first published in 1920. An interstellar voyage is the framework for a narrative of a journey through fantastic landscapes. The story is set at Tormance, an imaginary planet orbiting Arcturus, which in the novel is a binary star system, consisting of the stars Branchspell and Alppain. The lands through which the characters travel represent philosophical systems or states of mind as the main character, Maskull, searches for the meaning of life. The book combines fantasy, philosophy, and science fiction in an exploration of the nature of good and evil and their relationship with existence. Described by critic, novelist, and philosopher Colin Wilson as the "greatest novel of the twentieth century", it was a central influence on C. S. Lewis' Space Trilogy, and through him on J. R. R. Tolkien, who said he read the book "with avidity". Clive Barker called it "a masterpiece" and "an extraordinary work ... quite magnificent".

Out of the Silent Planet is a science fiction novel by the British author C. S. Lewis, first published in 1938 by John Lane, The Bodley Head. Two sequels were published in 1943 and 1945, completing the Space Trilogy.