This is one of the smartest books I've ever read.
It covers all the scales: from the ideal mineral composition of garden soils to the pulses of biological expansion that flourish between ice ages. How the high productivity at the edge of a garden bed is analogous to the high productivity at the fringes of culture. It's a book of theory and philosophy in one sense, but this is philosophy that feels like a supple tool in the hand. Holmgren never lets you forget how the details on the ground are examples of larger interlocking processes, and likewise no abstract concept is presented without clear examples of their relevance and application.
It doesn't teach you how to build a permaculture garden, but it tells you what to keep in mind in order to do it right, and imparts the framework you'll need to interpret your ongoing progress in light of all the bigger pictures.
I would even recommend this book to people who will never make a garden, because the principles and observations it contains are vital to the whole human story. It's also the best, most well-rounded book on peak oil and energy descent that I can think of.
It's not perfect, but this is important work, and not many people are doing it, especially with the insight, clarity, and commitment that Holmgren offers here.