Manly. P. Hall is a renowned scholar in Freemason circles and was a 33 degree Scottish Rite Freemason himself.
Here's what a Freemason source says about that book-
Like no other book of the twentieth century, Manly P. Hall’s legendary The Secret Teachings of All Ages is a codex to the ancient occult and esoteric traditions of the world. Students of hidden wisdom, ancient symbols, and arcane practices treasure Hall’s magnum opus above all other works.
Manly. P. Hall is a renowned scholar in Freemason circles and was a 33 degree Scottish Rite Freemason himself.
Here's what a Freemason source says about that book-
https://freemasoninformation.com/masonictraveler/manly-p-hall-freemason-and-philosopher/