I use a simple measure for the greatness of a book: The number of times per chapter that I must lay it down saying "wow, that means ... " or simply to reflect on what I read to try and ensure I've internalized the message received. By both counts this 1972 book is, quite simply, great - a verdict I'm willing to state just half way through as each chapter has multiple such moments and each chapter is better than the one before. It is unfortunate that it is out of print - it puts almost all of present day efforts, with their one or two chapters of meat - if that - followed by relentless servings of pablum, to shame. If you come across it pick it up!