Isn't this a Neo-Pagan book? Sorry, but I have no respect for Neo-Paganism because, quite frankly, they lie.
They falisify history, claiming to be the continuation of Old Paganism, but the truth is that the Old Paganism died out, and there was no one to teach it. So the new Pagans did the best they could with the limited information in books, and added a whole bunch of stuff that they simply made up out of whole cloth.
In many cases, they left out stuff that they found unappealing, such as human sacrifice by the Celts in Central Europe.
And they don't actually believe in magick, which works every time. Instead they believe in magick as a form of prayer, which may or may not work. They even encourage their members to make up their own magick spells, which simply wouldn't happen if they truly believed in the integrity of magick.