This book details all kinds of historical Yantras as revealed in various Vedas (historic Hindu scriptures). Yantras are cosmic machines which directs energies to the human body/mind to attain various psychic states. The author dwells deeply in to the philosophy behind it, which in essence is Hinduism. Understanding the Hindu concept of the world, the cosmos and the human being is the key to unlocking the power of Yantra. A reader who is not exposed to Eastern religious philosophies will find it difficult to comprehend the description of concepts behind the Yantra.
This book has many illustrations of historic Yantras and details of the significance of its geometric drawings. I liked this book for the depth of analysis and the description of underlying concepts. Please note that this is NOT an instruction work book on Yantras which details about how to make a Yantra.
One disappointing fact is that the author uses little space to describe Occult Yantras which are commonly used by ordinary people for protection, healing and power. The Sri Yantra, which enables a person to attain higher states is described in detail. Overall this book gave me indepth knowledge about the working of a Yantra - the energized cosmic machine.