"Eating Animals" by Jonathan Safran Foer

By the novelist who wrote "Everything is Illuminated" and "Extremely Loud and Incredibly Close" - this book tackles so many angles related to eating animals. Though it doesn't really get much into the vegan vs. vegetarian discussion.
Nevertheless, a compelling read - and I now know quite a bit about factory farming - what I wish every American would learn about as well. If you can really know what goes on in factory farming and are still OK eating their products, more power to you!