The author solves the cases in the best tradition of his idol, Sherlock Holmes. Occasionally, Dr. Siegel spent an inordinate amount of time searching for the origins of his patients' symptoms. Hopefully, he didn't charge his patients by the hour as he placed himself into sometimes very long, uncomfortable and even dangerous environments in an attempt to solve or understand the presented case.
My dictionary defines a hallucination as "an apparent perception of an external object when no such object is present." During deep primal relivings, many of us have had visual "hallucinations." Would a visual primal qualify as a hallucination? I don't want to nit-pick, but I don't believe it does, as the stored image is already in the brain.
I think that this book would be of interest to anyone curious about the origins and characteristics of hallucinations. Fire In the Brain is an exciting and entertaining book.