OK, this is a weird book. It's a perfect example of late 19th-early 20th century esoteric speculation that makes weak & tenuous connections between a diverse range of mystical ideas, personalities, & texts. Sometimes inspired by purported cognate syllables and hand gestures that appear similar in ancient art as well as Jewish and Masonic practices & signs.
The thing is, I kinda buy into it in this book. When I first read it (it must have been the first edition, as it was in the 70s, or very early 80s, and this edition is copyrighted 1988), it perfectly exemplified subtle correspondences I was already making between Hebrew Qabalah and the Younger Edda of Norse mythology. Adding Freemasonry into the mix completed the odd foreshadowing of the central pillars of my later adult life.
The first time I read this was around the time I first read Manly P. Hall's "Secret Teachings of All Ages", and I've been an unabashed syncretist ever since. It's a wild & crazy journey from one speculative connection to another.... But it's one of the better, more worthwhile examples of the genre.