I haven't read it myself, but Amazon.com has some interesting reviews of it:
http://www.amazon.com/Omnivores-Dilemma-Michael-Pollan/dp/1594200823

I found this one particularly helpful:

A Flawed Masterpiece, April 26, 2006

Reviewer:  Erik Marcus "Author of Meat Market: Animals, Ethics, and Money" (Ithaca, NY USA)

The Omnivore's Dilemma is a celebration of alternative agriculture that every vegetarian should read. Michael Pollan's account of modern-day food production is beautifully written, and demands the attention of everyone who cares about what, or who, they eat. This is easily among the most important books on food written this decade. Happily, Pollan's disgust with factory farming is clear, and The Omnivore's Dilemma is largely a quest to bring ethics into animal agriculture.

Unfortunately, the superior quality of Pollan's writing only makes the book's flaws all the more glaring. The Omnivore's Dilemma contains numerous minor and forgivable lapses:
*Pollan spends three pages writing about Omega 3s, and the potential for grass-fed beef and free-range eggs to provide this elusive nutrient. Yet he never so much as mentions flax seeds, which are by far the cheapest and cleanest source of Omega 3s.
*He writes that, "...eggs and milk can be coaxed from animals without hurting or killing them-or so I at least thought." Whatever he may have once thought, he never gets around to informing readers that every commercially produced layer hen and dairy cow-even if free-range or organically fed-is sent to slaughter.
*He even suggests that if all Americans went vegetarian, "it isn't at all clear that the total number of animals killed each year would necessarily decline." This argument was first made by Oregon University agriculture professor Steven Davis, and has since been thoroughly debunked by Gaverick Matheny.</ul>

These lapses can easily be remedied with short rebuttals. Not so with one of the book's main and most problematic themes: the idea that one small farm in Virginia might serve as a template for enlightened agriculture. The Omnivore's Dilemma is largely a hagiography of Joel Salatin, the owner of Polyface farm. Salatin's lifework is admittedly remarkable. He's taken virtually all the overt cruelty-but alas, none of the slaughter-out of his egg, chicken, and beef operations. What's more, Salatin has found a way to raise these animals without drugs or pesticides. Through farming practices that radically depart from convention, it appears that Salatin's brand of animal agriculture enriches rather than depletes his soil with each passing year.

Most vegetarians take for granted that eating animals is akin to buying a Hummer, removing its catalytic converter, and using the vehicle to cart around nuclear waste. Pollan's book convincingly shows that animal agriculture can, in fact, operate in a way that respects the environment. For a reader who's acquainted with the staggering wastefulness of animal agriculture, it's hard not to get caught up in Pollan's account of the Polyface alternative.

What Polyface has accomplished is a genuine achievement. However, Pollan never points out that there's a reason why Polyface is plunked down in rural Virginia-hardly the heart of cattle country. This model of farming could simply never be transplanted to the arid, near-dessert landscape of America's western states-the region that produces nearly all American beef. It's one thing to practice boutique farming and to raise 50 grass-fed cattle a year on lush, rain-soaked land in rural Virginia. It's quite another to imply that Polyface could be anything like a model for transforming America's beef industry. You simply can't scale up what's happening on a 50-steer farm in Virginia to positively transform the way that more than 20 million cattle are raised in the American West.

Michael Pollan is a talented writer, and had he only put this manuscript out for proper review this book could have been a masterpiece. Despite its flaws, The Omnivore's Dilemma deserves the attention of everyone who cares about animal cruelty. Nowhere is the case for eating animal products made so persuasively and thoughtfully. Yet the book's shortcomings demand some prerequisite reading-otherwise the reader may succumb to the same lapses in thinking that overcame Pollan.

Reprinted with permission. First published by VegNews magazine, May/June 2006