This book was very interesting, as it really dived into what we know about the lives of these great people.  Besides the religions they started, and the traditions surrounding that, there isn’t much in the way of written records of their lives.  The written records also tended to be written years to centuries after their lives.  The similarities in their teachings was also interesting, with the Buddha being the most different.  All the others were dealing with how to live well with others and how to have good lives.  The Buddha taught about how to let go of life, and not worry about earthly things anymore.  The others taught variations and specific instances of the golden rule.

Audible Link