Frater Acher has certainly become one of the most important authors in the "serious" occult community, first through his blog, later in the last years through his books. Again, as with the other two installments in the trilogy "holy Heretics" comprises the last part of, his voice is gentle but of an analytical clarity and precision which runs in a most pleasurable way against the often obfuscating nature of much occult scripture. His work is that of enlightening, scrutinizing sources, demonstrating their relevance and making them workable in a contemporary context without watering down. the book is structured in two main parts, the first being "Mysticism", the second "Magic" with accompanying analysis and practice. If you know his other works or maybe McCarthies "Quareia"-course you broadly know, what to expect here.
Note: I am quite sure, Hildegard from Bingen wouldn't share his interpretation of her works, at the same time I'm much more with Acher on the subject of balance, so I don't hold that against this book.