Well, the math today is way more advanced and I am curious what would Pythagoras or the other ancient teachers say about the mystical implications of our mathematical knowledge.
Some books that you may find interesting:
Tuning, timbre, spectrum, scale - W. Sethares (music related, there are discussions about Pythagoras and his scale, also other traditional JI scales in it)
Kappraff, J. "Connections: The Geometric Bridge between Art and Science
Kappraff, J. “Beyond Measure: Essays in Nature Myth, and Number (This guy is math professor and has many other similar books, but I've only these two and they are very good.)
The Math Book: From Pythagoras to the 57th Dimension, 250 Milestones in the History of Mathematics - C. A. Pickover