Kaplan's classic work in which he demonstrates how many advanced meditative techniques were used by the kabbalists. Aryeh Kaplan born in the Bronx, NY was a noted American rabbi and author, who had an MS in physics. In researching his books, Rabbi Kaplan once remarked: "I use my physics background to analyze and systematize data, very much as a physicist would deal with physical reality. A great primer for those not interested in pop Kabbalah books. Kaplan practiced what he wrote and it shows. A great text for serious students and those who want real Kabbalah.

Excellent introduction to the history of Kabbalah and how we can apply to our everyday lives.

This book is not as potentially rewarding to a beginner but requires some knowledge before reading. It is a good idea to know a little bit about the various famed Rabbis, who they were, where they lived, and what they were famous for. It is also a good idea to have some reasonable level of experience of meditation and prayer, and to have had some direct experience with devekut and feel comfortable and validated in one's experience. It is also good to have a basic grounding in theoretical Kaballah and the sefirot. Maybe more than basic.

So, if the above paragraph describes you, this book is an astoundingly great book. First of all, the historical timeline of the rabbis and their interelationships is easy to understand and is very synthetic. I also found the presentation of Abulafia's permutation methods to be easily understandable and surprisingly easy to put into practice (the first one anyway). I can hear the angels now whining about my newfound attempts to permute the Tetragrammation, who do these puny humans think they are anyway?

I have edited this review as I recently finished the book. This is a phenomenal book. The first text that I have read which provides an organized understanding of the timeline and rabbinic players in the ongoing tradition of Jewish mysticism. From Abulafia to Cordovero to Reb Vitale to the Ari and the Baal Shem Tov, all of the important rabbinic figures, their contributions and their historical relevance are coherently summarized. I wish that I had read this book a lot earlier. But even better, Kaplan provides a summary of the yichudim and meditations used by the masters here in the text. Although there is a slightly amusing warning in the beginning of the text that you cannot read the text in a bathroom because it contains the names of God, there emerges a much clearer understanding why the publishing of this material can be considered potentially dangerous. The clear meaning of the commandment regarding not taking God's name in vain is apparent after reading this book. The use of these meditations and yichudim without near perfect intent by people is the ultimate meaning of taking God's name in vain. In other words, it is misuse of the names of God. Used in the correct manner, the book is fabulous.