Manly Palmer Hall (March 18, 1901 – August 29, 1990) was a Canadian-born author and mystic. He is perhaps most famous for his work The Secret Teachings of All Ages: An Encyclopedic Outline of Masonic, Hermetic, Qabbalistic and Rosicrucian Symbolical Philosophy, which is widely regarded as his magnum opus, and which he published at the age of 25 (or 27, 1928)
For reference, here is the introduction: The Secret Teachings of All Ages
YouTube Audio version of the entire book broken into ~10-minute segments. They play back to back:
Also for reference here are quite a few Audio Lectures by Manly P. Hall
