Thirty Years Among the Dead, first published in 1924, details Swedish-American GP and psychiatrist Carl Wickland's experiences as a psychical researcher.
After moving to California in 1918, Wickland began to turn away from conventional medical psychology and moved toward the belief that psychiatric illnesses were the result of influence by spirits of the dead. He came to believe that a large number of his patients had become possessed by what he called "obsessing spirits", and that low-voltage electric shocks could dislodge them. His wife Anna acted as a medium to guide them to "progress in the spirit world".
Spiritualists considered him an authority on "destructive spirits", prompting Wickland to write this book.