Alan Gauld 
The Founders of Psychical Research [PDF ebook] 

Originally published in 1968 The Founders of Psychical Research is centred upon the lives and work of Henry Sidgwick, Edmund Gurney and Frederic Myers – prominent in the Society for Psychical Research (S.P.R) – during its early years: it is not a history of the Society. It passes over important aspects of the S.P.R.’s story and deals at some length with matters quite outside it. The book frequently gives accounts of ‘paranormal’ phenomena which if indeed they occurred, would not be explainable through any recognisable hypothesis, but are treated throughout as unexplained.