Brood of the Witch-Queen by Sax Rohmer

Although best known as the creator of the Fu-Manchu series of mystery novels, British author Arthur Henry Sarsfield Ward (who usually wrote under the pseudonym Sax Rohmer) also penned a number of science fiction, fantasy, and supernatural novels. Long himself associated with the occult, Rohmer brings captivating depth and detail to his story of a dabbler in the supernatural whose dark interests spin out of control -- with tragic results.