This work attempts to be an introduction to sustainable farming. The author's assertion (well supported by the evidence he cites) is that our current agricultural model is failing, and that we need to move away from a system built on annual plants, and towards a system built on perennial growth. This is permanent agriculture, or "permaculture". His model for this is an idealized, carefully structured combination of plants, or "polyculture" for food, fuel, and animal forage. In his words: "[w]hat we are doing is designing an agricultural system that closely mimics the savanna in its structure, the species mix, and in ecological function."
This model has been outlined in pieces in other books. Much of his ideas about livestock forage are similar to what Joel Salatin writes, though Shepard is less strident, and more open to the idea of a vegetarian diet. He spends a great deal of time demonstrating with chart and figures how, exactly, a more perennial agricultural model can generate more nutritious calories per acre than the current single crop. But the graphs do not overwhelm.
I was pleased by the concrete examples in the book. Shepard demonstrates, in color pictures and with facts and figures, the viability of a farm based on permaculture principles. He gives tree spacings, plant yields, and grazing techniques. He explains the proper ratio of cows to sheep, for instance. However I was expecting a lot more details regarding plant choices, harvesting techniques, etc. What can be said for Shepard is that he stays on point better than, and is more accessible than, Bill Mollison, who has a tendency to wax philosophical. That said, Permaculture: A Designers' Manual remains a better resource than Restoration Agriculture.
Occasionally his hypotheses are supported only by assertion. For example, he states outright "every culture built on annual crops has failed". This is either false, if you take into account current civilization, or unverifiable, if you assert, as the author does, that our culture is doomed to fail. Additionally, while he describes growing vegetables in places, he also seems to state that this will be phased out as the forest matures. I don't think any system of agriculture that phases out vegetables can be entirely nutritious. But this aspect of the book is not entirely clear, and I may be misreading the author's intention.
My one concern about permaculture is that the staple crops derived from trees are not as easily palatable. Certainly anyone who has eaten "bread" from acorn flour will be unlikely to prefer it to bread from whole-wheat flour. So a place will likely remain in society for grain crops. But we could all do well to read this book and encourage farmers and landowners to start implementing these principles. If you consider that the nutrition in, say, an ear of corn has to come from somewhere, and that "somewhere" is largely out of the ground, and out of fertilizers derived from petroleum, you can easily see that our current agricultural model is essentially mining the topsoil. Since current practices do not build topsoil, and at some point, maybe in 10 years, maybe in 100 years, we are going to see petroleum reserves stable off and eventually decline, we are not in a sustainable cycle of production. Whatever your political conviction, you should think about the issues addressed here.
Overall, however, a very well written distillation of the classics of permaculture, plus examples of how well it works, and a plan to implement it on a large scale across North America. I think the target audience here is not the well read, inspired permaculture enthusiast, but instead the average person who has not heard of this concept. For that purpose, he succeeds well at introducing concepts, and demonstrating how well they work. Go to other sources to get the details though.