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place in post-war England, and they specifically bring in references to Tolkien's legendarium (at that time largely unpublished) and treats these references as primary fact within Lewis's fiction.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:
Warwick
J. R. R. Tolkien seems to have been very influenced by Warwick (where he was married in the Catholic Church of Saint Mary Immaculate) and by its Mercian connections: Lynn Forest-Hill, in an article in the "Times Literary Supplement" (TLS 8 July 2005 pp 12–13) argues cogently that two important settlements in Tolkien's work were modelled on Warwick — Edoras closely on the early town, and Minas Tirith more remotely on the Norman; and that aspects of the plot of "The Lord of the Rings" are paralleled in the romance known as Guy of Warwick. Christopher Tolkien, in "The Book of Lost Tales", stated that Kortirion, the main city of Tol Eressëa, "would become in after days Warwick."