Okay look first off: it is a bummer when you get through 118 pages of an occult book only to learn that all queer and intersex people are universally banned from initiation into magical practices, except of course for "phallic rites and black magic, where such things have a use." Fuck you very much, Dion Fortune! Also: ludicrous early-twentieth-century "scientific" racism, except in terms of magical practices, ugh, but at least not very much of it.
But aside from that, what is there even to say about this book? I have no idea how one even decides whether it's good or not, short of like--actually entering into a slow process of magical initiation along her lines. I will say that as these books go, there was a pretty close tracking between Fortune talking about say, the Lords of Atlantis and how their Manu Narada was responsible for the organization of human spirit into the conscious mind, me thinking "Wait a minute, Dion Fortune, Atlantis, really, what the heck," and Fortune writing that of course it'd be stupid to actually believe any of this made-up sounding stuff about Atlantis so don't worry about it too much. So if it's mystical folderol, it is at least mystical folderol that does some nontrivial work toward "convincing the skeptic" in a way that I appreciate. Also points for saying that maybe before you study magic you should go off and study physics, basic logic, and the history of philosophy so that you do not say dumb stuff. It is a magic book for those of us who are deeply suspicious of magic books I guess.