John Moriarty is a one of a kind writer. This book, while it might be difficult on first reading because of his many allusions to a huge swathe of literature, is well worth the effort. John is talking about one thing only, the path to enlightenment, spiritual development, and he uses his great erudition to support what he is saying. All traditions and cultures have had and have their own mythology or way to speaking about this matter. John decodes these mythologies for us. The Perennial Wisdom is John's metier.
It takes more than one reading. My experience of this book was that it had a cumulative effect on me, a gradual coming to understand and absorb what he was saying. It is a very powerful book, I think.