Darker than you think (Fantasy Masterworks)

Blurb

Darker Than You Think by Jack Williamson, originally a novelette, was expanded into novel length and published by Fantasy Press in 1948. The short version was published Unknown in 1940. It was notably reprinted by UK-based Orion Books in 2003 as volume 38 of their Fantasy Masterworks series. It can be classed as contemporary fantasy and urban fantasy, though these were not yet clearly defined categories at the time it was written.