Here is a very brief, idiosyncratic, incomplete bibliography of food ethics. These are all books I own, though I haven’t read all of them cover-to-cover. No endorsement is implied except where specifically noted.
Just Food: Where Locavores Get It Wrong and How We Can Truly Eat Responsibly, by James E. McWilliams [This book has been roundly criticized by locavores, but I found it useful.]
The Omnivore’s Dilemma: A Natural History of Four Meals, by Michael Pollan
In Defense of Food: An Eater’s Manifesto, by Michael Pollan [I like Pollan's writing, and he's highly informative, but I found him less useful than McWilliams, especially as an intro to the debates.]
Animal Liberation: The Definitive Classic of the Animal Movement, by Peter Singer [Singer is a very smart philosopher, though I disagree with most of what he says.]
Food Biotechnology in Ethical Perspective, by Paul B. Thompson [very smart book, recommended without reservation]
Before Dinner: Philosophy and Ethics of Food by M. Korthals
Labeling Genetically Modified Food: The Philosophical and Legal Debate, Paul Weirich (Editor)
[If you know of relevant books I should read, feel free to email me.]
If you’re looking for books on ethics more generally, check out the recommendations at my EthicsWeb Bookstore.