From the description at Amazon.com and probably the back cover of the book also:
“Widely recognized as one of the most inventive science fiction writers of all time, Philip K. Dick is an author whose literary sophistication elevated the sci-fi genre into the storytelling powerhouse it is today. His works, known for their portrayals of simulated realities interspersed with universal and philosophical themes, have become enormously influential among writers of all genres and have inspired numerous television and film adaptations, including the 1982 cult classic Blade Runner.
Dick’s personal life matched the dramatic intensity of his most beloved works. Beginning with the tragic death of his twin sister, his life took on a fantastical, science fiction-like quality when, in 1974, he had what some consider to be a psychotic episode and what others believe to be a mystical experience. According to Dick, a pink light beamed psychic information into his brain, awakening memories of a past life as an ancient Christian revolutionary and granting him contact with time-traveling extraterrestrials. He had visions of scenes from ancient Rome superimposed over his neighborhood in suburban San Francisco, and later on, attempted to warn local police that he was a machine programmed to self-destruct. As a result, Philip K. Dick spent the rest of his life trying to fathom the meaning of what he called his “divine madness.” Was it schizophrenia? Or a genuine religious experience?
In The Divine Madness of Philip K. Dick, clinical psychologist Kyle Arnold probes the fascinating mystery of Dick’s heart and mind, and shows readers how early traumas opened Dick to profound spiritual experiences while also predisposing him toward drug dependency and violence. Disputing the myth that Dick had schizophrenia, Arnold contends that Dick’s well-known paranoia was caused by his addiction to speed. Despite Dick’s paranoia, his divine madness was not a sign of mental illness, but a powerful spiritual experience conveyed in the images of science fiction.”