“The Great God Pan” is a novella by Welsh writer Arthur Machen. Now his most celebrated work, it was broadly condemned by the media as horrific and degenerate due to its sexual content and decadent style when first published. The plot revolves around a man called Clarke who agrees to witness an odd experiment performed by his friend, Dr. Raymond in an attempt to open a person's mind to the spiritual world. After some minor brain surgery, Mary—the test subject—awakens to utter horror before quickly becoming "a hopeless idiot". Arthur Machen (1863 – 1947) was a Welsh author and renowned mystic during the 1890s and early 20th century who garnered literary acclaim for his contributions to the supernatural, horror, and fantasy fiction genres. His seminal novella “The Great God Pan” (1890) has become a classic of horror fiction, with Stephen King describing it as one of the best horror stories ever written in the English language. Other notable fans of his gruesome tales include William Butler Yeats and Arthur Conan Doyle; and his work has been compared to that of Robert Louis Stevenson, Bram Stoker, and Oscar Wilde. Many vintage books such as this are increasingly scarce and expensive. It is with this in mind that we are republishing this volume now in an affordable, modern, high-quality edition complete with a specially-commissioned new biography of the author.