I found this book to be very well written. The author is knowledgeable on the subject and as plus mentions Franz Bardon, giving readers a chance to look at the work of an earlier occult author. Konstantinos provides readers a thorough examination of summoning spirits, including several different ways of evocation and exercises that can be used by the beginner or adept to ground him- or herself and get a working knowledge of how to evoke before the actual evocations begin. He also provides a list of spirits the magician might wish to work with.
However, while I liked this book overall I did find the emphasis on Judeo-Christianity to be a bit much. Granted much of the tradition of evocation is centred around those religions, however I wish the author would’ve researched other magick systems such as demonolatry so that he could present alternative ways of evocation that don’t involve calling on the Judeo-Christian god. At the least I would’ve liked to have seen a framework provided for magicians that might not be comfortable working with Judeo-Christian spirits