The Web is a treasure of books and other media in the public domain, and sites like archive.org and gutenberg.org offer texts in a number of different formats. For purveyors of weird and early horror fiction, there are a number of full texts available. Below is a small sampling of some of my favorites.
The Great God Pan-- A classic tale of ancient powers infiltrating modernity
The White People-- A strange unsettling story of a young girl describing arcane and secret rites
The Willows--My favorite weird tale, filled with religious dread.
The Call of Cthulhu--"We live on a placid island of ignorance in the midst of black seas of infinity, and it was not meant that we should voyage far."
Clark Ashton Smith
The Immortals of Mercury-- One of Smith's science fiction tales, but as weird as anything he has done, where "There were long, tediously winding tunnels that went down into Cimmerian depth, or climbed at acolivitous angles."