"Many Lives, Many Masters" is a book by Brian L. Weiss, a psychiatrist who explores the concept of reincarnation. The narrative follows his experiences with a patient named Catherine, who, during therapy sessions, begins to recall past lives. These revelations lead to profound insights about life, death, and the soul's journey. The book combines elements of psychology and spirituality, suggesting that understanding past lives can help individuals heal from present issues. Weiss presents case studies and therapeutic techniques, emphasizing the importance of love and forgiveness in personal growth and spiritual development.