Nice book; good -- even (in part) a thrilling read. Only problem is -- it is wrong.
If you're interested in this topic, you must read Ivan Linforth's Arts of Orpheus -- which is a masterpiece. Unfortunately, it cannot really be read by a reader who does not have Greek.
That is a great advantage with Guthrie -- you don't need to know anything to read it; and precisely what is wrong with so much Classical scholarship today.