The House on the Borderland

William Hope Hodgson's "cosmic horror" classic continues the Haunted Library of Horror Classics series.
In a ruined house at the edge of an abyss lies the diary of a madman…
Two friends on a fishing trip make an unsettling discovery when the river they've been following abruptly ends and reappears some 100 feet below the edge of an abyss. If that wasn't unnerving enough, the river runs along the remains of an oddly shaped house, half-swallowed by the pit.
Within the ruins, they discover the moldering journal of an unidentified man—the Recluse—who had lived in the house years ago. Its pages reveal the man's apparent descent into madness—why else would he chronicle haunted visions, trips to other dimensions, and attacks by swine-like creatures that have followed him home? After a horrific vision in which he witnesses the end of the earth and time itself, the Recluse awakens in his study to find nothing has changed—except that his dog has dissolved into a pile of dust. And then the "swine things" return...
Introduced by modern horror master Ramsey Campbell as "an enduring classic of cosmic terror," The House on the Borderland has inspired dozens of other classic horror novels and indelibly changed the genre. Influencing writers from H.P. Lovecraft to Terry Pratchett, this 1908 masterpiece shucks the conventions of Gothic horror and presents an eerie mix of sci-fi, fantasy, and the supernatural.