"Vril" is a mysterious energy used by Lytton's subterranean race -- refugees from the deluge that submerged Atlantis -- to power their advanced civilization. Generations of occultists have mistaken this bit of business for something other than fiction; and still more generations of science fiction writers have recycled the novel's plot. Vril is a book of strong interest to anyone doing a scholarly study of the evolution of SF; it's also a novel well worth reading in its own right.