Etidorhpa is an early science fiction novel depicting a man's descent into the bowels of the Earth at the instigation of a mysterious secret society - it is presented here complete with the original illustrations.

Llewyllyn Drury is visited by a mysterious old man whose defining physical feature is his large, protruding forehead. The man offers to tell his story, promising his life and knowledge is worth writing down. As the man displays certain enthralling and supernatural powers, Drury takes on the task - Etidorhpa is this story, interspersed with pauses wherein Drury questions his strange guest.

John Uri Lloyd was a popular author of mystery and science fiction books. His profession however was pharmacology, with his specialism being herbal medicines and ethnobotanicals. The presence of giant mushrooms in one part of the story, plus the various fantastical elements described, have led some readers to speculate that the author's knowledge of mind-altering substances influenced Etidorhpa's plotting.