Abraham Merritt 
The Face in the Abyss [EPUB ebook] 

The Face in the Abyss‘ is a fantasy novel written by Abraham Merritt, an American author known for his works in the early 20th century. First published in 1923, the novel combines elements of adventure, horror, and science fiction in a tale set in a fantastical world.
The story follows the journey of Nicholas Graydon, an explorer and archaeologist, who stumbles upon a hidden civilization beneath the Earth’s surface. This underground world, known as Zarkandhu, is filled with strange creatures, ancient secrets, and a cosmic evil that threatens both Zarkandhu and the surface world. Graydon becomes embroiled in a dangerous quest to save both realms from the impending doom.