This Shelf Indulgence review of Hallucinations, by Oliver Sacks, came out of my research for one of the Ashley Dyer novels. Sacks, a professor of neurology, turns his exceptional eye on the phenomenon in this fascinating book. Covering aspects as diverse as epileptic seizures, Out of Body experiences, Post Traumatic Stress Disorder (PTSD), migraine auras and the weirdness of coming to face-to-face with your doppelganger, Sacks explains that hallucinations are far f...