Weiss is the author of the text, an American psychiatrist, and a past-life regression pioneer. A scientific skeptic by training, Weiss’s doubts dissolved as he encountered what seemed to him to be compelling evidence for reincarnation. He has a wife, Carole, and a daughter, Amy, who has also published on the topic of past life research. Weiss was the Head of Psychiatry at the Mount Sinai Medical Center in Miami, and it is during this phase of his career that the events of this book unfold. He has treated thousands of patients using past life regression.

Many Lives, Many Masters outlines the author’s transformative experiences treating a patient named Catherine. Together, they access a wealth of wisdom through Catherine’s hidden memories of living through dozens of lifetimes since ancient times. Over time, Weiss receives messages from spiritual beings known as Masters, who explain that the experiences Weiss and Catherine are having during their sessions are primarily for the benefit of Weiss, who is meant to continue learning about reincarnation and help as many people around the world as possible. Now, Weiss conducts seminars and workshops around the world to help and educate people using the power of past-life therapy.