Vril, the Power of the Coming Race (Unabridged‪)‬

Vril, the Power of the Coming Race (1870) by Edward Bulwer-Lytton is an early science fiction novel. The setting is a strange subterranean world inhabited by beautiful entities that resemble the angels described in scripture. The advanced beings known as Vril-ya live underground - using the mysterious "Vril" as an energy source - but intend to reclaim the surface of the earth as their own. The narrator ends up deep inside the Earth via a natural chasm in a mine shaft. He is rescued by the Vril-ya, an advanced race that use telepathic powers, fly with artificial wings, are served by automata, and possess formidable weapons. After a long stay, things go wrong and the protagonist escapes back to the surface with the help of Zee, one of the Vril-ya.