I've read many introductory books on Kabbalah but this is by far the most comprehensive. It is one of the few books that emphasises the central role of the Hebrew letters and language (the 'Loshon Kodesh' or Holy Speech) which are thought to have been the tools of creation itself.
There are clear explanations of difficult subject matters such as the Tree of Life, the Sefirot (Divine attributes) and some fascinating material on the famous Golem of Prague (who legend has it was animated and brought to life using the Divine names). Clearly Professor Lancaster is writing not simply from a scholarly perspective but also has first hand experience of some of the meditative techniques described.
A remarkable achievement, which deserves to be a spiritual bestseller.