Robert Hugh Benson 
Necromancers [EPUB ebook] 

In THE NECROMANCERS Robert Hugh Benson sets out to expose the dangers of "Spiritism, " interest in which had reached epidemic proportions by the early twentieth century. C. C. Martindale, S.J. commented that, "It is in THE NECROMANCERS that he brings all his heavy artillery to bear on his professed enemy. Here again the uncanny enters, but rises to the heroic level, and achieves the horrible; and I will confess that I can think of no book which reaches so high a pitch of horror, unaided by alien elements." (Goodreads)