Books like The Moon Pool by A. Merritt

The Moon Pool, in novel form, is a combination and fix-up of two previously-published short stories: "The Moon Pool" and "Conquest of the Moon Pool." Initially serialized in All-Story Weekly, Merritt made the interesting choice of framing the novel as a sort of scientific retelling, going so far as to include footnotes from fictional scientists, to give this completely fantastic work an air of authenticity.

In it we find the adventuresome botanist William T. Goodwin embarking on a quest to help his friend Throckmortin, whose wife and friends have fallen victim to a mysterious temple ruin on a remote South Pacific island. A series of coincidences provides Goodwin with a colorful cast of accompanying adventurers, and they soon find themselves in a mysterious futuristic underworld.

The Moon Pool is an important entry in the Lost World genre, in no small part because it was a significant influence on H. P. Lovecraft—hints of The Moon Pool can be seen in his short story "The Call of Cthulhu," and hints of Merritt’s Nan-Madol can be seen in Lovecraft’s R’lyeh.

Today, The Moon Pool is a pulp classic, featuring many of the themes, tropes, and archetypes that characterized so many of the pulp adventure works of the era.