This is an indictment of animal foods on environmental grounds. As such, it is in a category by itself, and this is an important reason for recommending this. It is well researched and has a lot of material that you can't find elsewhere, including some material that I hadn't seen anywhere myself -- and I follow this topic rather closely.
He talks about a number of important environmental issues: climate change (which he calls "global warming"), the destruction of rainforests, desertification and soil erosion, species diversity, water depletion and pollution, overfishing, and fish farms. One thing that I especially liked is that he is not taken in by the "grass fed beef" arguments. He also adds chapters on rationalizations for meat-eating, health aspects of meat-eating, and ethical aspects of meat-eating.
The main weaknesses of the book are literary, not in the material he presents. The book would have benefited from a strong editor. A lot of writers, including myself, have done much worse at their first draft. Back the manuscript comes with a lot of red marks through it and some comment like, "This is going to be a great book! But first we need you to cut about 100 pages." (Seriously.) But whoever published this book (Landgon Street Press) either did not edit this book at all or did a really lousy job.
This book's problem is not the length; actually it could be longer. The first thing I, as an amateur editor, would say is that he needs to identify his audience. At the beginning of the book, Oppenlander says he is addressing two audiences: those somewhat aware that there is a connection between food and the environment (I think this means people who have read Michael Pollan), and those who are not aware at all -- the "comfortably unaware" of the title.
This won't do at all: he needs to decide on one audience or the other. I would vote for the first audience and make it a more technical type book, just because you can't popularize something that even the experts don't understand, and that's a key reason why information on this subject isn't better understood. We are the mercy of people like Michael Pollan, Al Gore, and Mark Bittman (great writers who don't quite understand what's going on food-wise) to explain things which actually no one has quite figured out. If he had chosen the second type of audience, I think he would have wound up with an updated and expanded version of the three chapters in John Robbins "The Food Revolution" which discuss the environment. As it is, he has just enough extra discussion and facts and figures to confuse the people in the second audience, but not enough to make the people in the first audience happy.
The second thing I would advise would be to ramp up the footnotes. A lot of his footnotes are just fine, but others aren't. Here's an example: on page 123 I read, "it would still require [using any system of pasture-fed beef] between two and twenty acres of land to support the growth of one cow." Wow! This is something that I've researched and for which I have never found a completely satisfactory answer (though I see that John Robbins mentions a similar figure briefly). I eagerly turn to the back to look at the footnote, and it reads: "USDA Economic Research Service." I think this means that he talked to someone in the USDA, in which case he should say something like "personal communication, August 23, 2009, with Joe Schmo of the USDA Economic Research Service." Or maybe it's on their web site? We are left clueless. (There's no bibliography.) In other cases, he gives the right reference but no page number. Here are some more examples: "Preventive Medicine, Nov. 1996," "Wikipedia.org" (I would at least cite the article name and the date), and just "Amazon Prosperity." Sometimes you can trace the source by looking at previous (more full) footnotes, but at other times, you can't.
I am going back and re-reading the whole thing and tracking down every last footnote (well, most of them). This is an important issue and we should be thinking about how to deal with the questions this book raises. The discussion of the environment in "The Food Revolution," probably its closest competitor, doesn't go into quite the detail that I'd like and is only three chapters (much of the book is a reprise of health and ethical issues). The decline of civilization is MUCH closer than anyone is thinking. See: "peak oil," "financial collapse," and "credit bubble," and we haven't even gotten to "climate change."
Civilization probably won't collapse, but a couple of more crises like that of 2008, and we may be all be much poorer and much less able to research all of this stuff. Life will go on, and if we're lucky the grid won't collapse right away, but we may never have the same information resources that we have, right now, and the political ability to deal effectively with these issues may also decline. If you care about these issues, then sure, critique the book; but go over each statement, read it for the information it contains, and try to figure out how this fits into the whole problem of ecological economics. Despite its shortcomings, there's no quicker way to get an overview of the key issues.