Hall was born in Peterborough, Ontario in 1901, had no university education, and published The Secret Teachings of All Ages in 1928, at twenty-seven, a folio encyclopedia of Western symbolism covering the mysteries, Freemasonry, Kabbalah, alchemy, Rosicrucianism, Pythagorean number and comparative religion, with colour plates by J. Augustus Knapp, funded by subscription. It has never gone out of print and it is the book through which an enormous number of people first encountered this material.
Its value is as a compendium of what the tradition believed about itself, assembled with real breadth and genuine affection. It is not a work of history and should not be used as one: it repeats the Egyptian origin of the tarot, ancient lineages for Freemasonry and Rosicrucianism, and a chain of initiatory transmission running from the Egyptian temples through Pythagoras to the modern lodges. None of that survives historical scrutiny, and Hall was reporting the tradition's self-understanding rather than testing it.
He founded the Philosophical Research Society in Los Angeles in 1934, lectured for six decades, and was made an honorary 33rd-degree Mason late in life. His death in 1990 was strange enough that it was investigated: he died at eighty-nine in circumstances involving a business associate, Daniel Fritz, and the case was reported as suspicious without any charge ever being brought. Louis Sahagun's biography sets out what is known.