The density of information often made me put the book to reflect, reconsider, analyze and resume. But the patterns are well introduced and used to follow the thread of thought without much lost.
I sometimes had the feeling that some aspects were flown (mediumship listed above) and which have earned can be a bit more interest. While others (significantly more) were very well covered (particularly on the concept of energy development in the environment, even though I have not necessarily 100% agreement on everything, but if not it would not funny).
Coté content, you can feel the clear thinking on the subject, how to consider the energies is well presented and can provide an excellent approach to those who have not yet thought about the subject and the field (and I think they are many). The thinking is clear, despite the complexity sometimes hidden by words, simple sentences and diagrams.
Clearly, this book provides in-depth work on the concept of purification, often flown and little understood, much less depth. And it is to have all library to (re) consider this methodology oh fundamental whatever the nature of your esoteric / spiritual journey.
The theoretical aspect is also balanced with practicality, with descriptive media, sometimes ... surprising.
My divergent views remained minor, a real substantive work, to read then.
Hagel