This book is written for the layman - consisting mostly of personal narratives, with very little in the way of actual scientific information. That's not necessarily a bad thing; the same approach works very well for Oliver Sacks (whose glowing praise is quoted on the back of the book). Unfortunately, Ronald Siegel is no Oliver Sacks, either in terms of storytelling ability or scientific credibility. Siegel recounts anecdotes of his research into hallucinatory phenomena - such as a teenage girl who still spends time with an imaginary friend, a woman whose experiences with DMT have left her with permanent auditory hallucinations, a man who lives with the ghost of his unborn daughter, and the imaginary companions of those lost alone at sea. It's an interesting read, but Siegel's academic integrity leaves something to be desired. His methods are sloppy, and though he assures us he doesn't believe in any of that paranormal mumbo-jumbo, he entertains said mumbo-jumbo a little too seriously - even going so far as to admit that his bookshelf includes titles on astrology and plant consciousness. He refers to his volunteer research subjects as "psychonauts", and expresses implicit sympathy with the drug culture of the 70s. All in all, I don't think Siegel is the best source of objective information on the subject.