If you are interested in Nyingma Dzogchen Tibetan Buddhism, or following its paths, this is an essential book. Keith Dowman's translation is idiosyncratic, and begins to betray his age. Words like 'zing' and 'glitch,' both of which he likes to use, rather lack resonance for many people now. One also has the sense that he is interested in comparisons between quantum field theory and Longchenpa: this line of thought was particularly fashionable in the 1970's and 1980's - it can be taken too far. Dowman is also greatly into the word, 'matrix.' All this said, provided you have a Buddhist teacher deeply embedded in the Nyingma lineage, and provided you are a practising Buddhist, meditating regularly, this book has much to offer you. I recommend it to English and German Longchen Foundation students.