Middle-earth
Another example is C. S. Lewis's "Space Trilogy," in which Earth is also called Middle-earth. Lewis's novels are situated at the approximate time of World War II, with the last novel, "That Hideous Strength," taking place in post-war England, and they specifically bring in references to Tolkien's legendarium (at that time largely unpublished) and treats these references as primary fact within Lewis's fiction. Merlin, of King Arthur fame, is treated as a successor to the Atlantis magic found within "Numinor" (Lewis's unintentional misspelling of Númenor), and similarities can also be found in the Quenya name for Númenor, which is "Atalantë," and Lewis specifically references the earth as Middle-earth twice, both in Chapter 13, "They Have Pulled Down Deep Heaven on Their Heads". Lewis's borrowings came directly from Tolkien himself: they were close friends and shared each other's literary creations. Lewis encouraged Tolkien to persevere with his Middle-earth writings.A small selection from the many books about Tolkien and his created world:
J. R. R. Tolkien
The Tolkiens had four children: John Francis Reuel Tolkien (17 November 1917 – 22 January 2003), Michael Hilary Reuel Tolkien (22 October 1920 – 27 February 1984), Christopher John Reuel Tolkien (born 21 November 1924) and Priscilla Mary Anne Reuel Tolkien (born 18 June 1929). Tolkien was very devoted to his children and sent them illustrated letters from Father Christmas when they were young. Each year more characters were added, such as the North Polar Bear (Father Christmas's helper), the Snow Man (his gardener), Ilbereth the elf (his secretary), and various other, minor characters. The major characters would relate tales of Father Christmas's battles against goblins who rode on bats and the various pranks committed by the North Polar Bear.