There are only a few decent training manuals for newcomers to magic, and many available at this time need serious updating. Many of us Gen-X magician cut our teeth on Paul Huson's Mastering Witchcraft, Crowley's AA system, and even Don Michael Kraig's Modern Magick. While I do not draw geometric symbols in the air anymore, they were useful starting points. That was what we had. Then many of us ventured into the ATR's at some point and learned from them.
I met Jason Miller online around 2004 in Yahoo Forums, where later authors would talk shop, including Moloch, Jake Stratton-Kent, Aaron Leitch, and others.
One day someone will put together a timeline of the (latest) magical revival, but at the time we were all coming out of 20th century magic and occultism, with may of us with years of experimentation in Chaos Magic, Goetia, Thelema, Hoodoo/Conjure, the ATR's , and finding ways to talk about our experiences with others. All the "traditions" out there were middling to terrible. We had to DIY the fuck out of it, as all magicians have to. Nobody is going to do the work for you, and you get better at magic by doing magic. Everything will work -well, until you meet spirits who have their own ideas and protocols, but that is another issue.
Fast forward to now and Jason is an author having to write for the broadest mass audience possible. It's just the reality of publishing world - and that mass audience are usually not folks as educated on magic, esotericism, and sorcery as the people here on Wizard Forums. It's easy to forget the people who came before you and take them for granted.
We had people like Moloch , who is a little older than us X'ers, who pointed out things to usefully explore. He had been exploring Conjure and Obeah from his time in Florida back when ceremonial magicians were calling Brujeria "stupid magic." It was Moloch who introduced us all to modern simplified "evocation magic" of New Avatar Power in 2004 or 2005, which later form a huge part of the GOM books.
I was somewhat surprised to find Jason and I work with many of the same spirits: St. Cyprian, the daimons, etc. My only quibble with him is he has way, way too many energy exercises in his work - which reads as super neo-pagan/modern "witchcraft" to me, but I think they are there to get newbies into the feeling they are doing something, so a 19th-century magical-electricity of Luminous Ether is the way to open their sense of the possible.
So while I do not use Jason's techniques - again too much visualizing glowing chi balls, and sparkly glitter rays for my taste - but from a New Thought / Chaos Magic perceptive there is nothing wrong with it. And if it get people moving then all good.