John Dee (1527-1608) led a remarkable life. He is well known to students of the Western Mysteries for introducing the Enochian Tablets to the world and also for the introducing various concepts of ritual.
Living at the time of Elizabeth I, he was respected in his own day as a scientist, geographer, antiquary and Hermetic philospher. But he was also reviled as an alchemist and magician whose spiritual revelations were looked on for three hundred years as a "work of darkness"
Re-released under Red Wheel's IBIS press, this book was originally written in the early 1900s, so the language (combined with the shakespearian-like quotes from Dee himself, three hundred years earlier) can be somewhat heavy going at times.
But the subject matter is interesting, particularly to those with an Hemertic or Gardnerian background, for in this book you will find ideas, concepts and 'spirit conversations' that lead to the Ritual of the Pentagram, Calling by Quarters and the Guardians of the Watchtowers.
As far as the language goes, if you can read Regardie and Gardner, you can read this. This book is a definite must-have for the serious hermetic student.