The notion that the Earth is hollow, or at least pitted with vast caverns and tunnel systems and populated by secretive, ancient civilisations who have spaceships, death rays and mind-control machines, became entrenched in popular mythology with the publication of a letter by Richard Shaver in the December 1943 issue of "Amazing Stories". The subject was an Elder Race of Teros and Deros, lost continents, and the Mantong alphabet—which Shaver believed to be the original language from which the root words of other languages were derived.
The Shaver Mystery came into its own with the March 1945 publication of "I Remember Lemuria", but by the end of 1948 the publishers of "Amazing Stories" had tired of these so-called 'true' stories—though the public certainly hadn't. Editor Ray Palmer quit to start up Fate magazine and continued to promote Shaver's stories. Released as a book in 1948, "I Remember Lemuria" quickly sold out and has been out of print ever since. Now it is reproduced in "Lost Continents & The Hollow Earth", along with another (co-authored) Shaver 'novel', titled The Return of Sathanas. The rather bizarre subject matter, though presented as fiction, prompted a flood of letters from people who claim to have had strange encounters with the Teros and Deros.
However, there is a substantial body of literature and circumstantial evidence which lend support to this kind of 'high strangeness', and author David Hatcher Childress devotes a chapter each to related areas of the Hollow Earth theory, UFO bases in Antarctica, tunnel systems beneath South America, the underground Himalayan city of Agartha, plus the history of the Shaver Mystery itself. Fringe fantasy, yes, but you never know: some of it may just be true!