I've been pouring over a LOT of information regarding veganism lately. The three books below are sort of my vegan bibles. So far, I have not had one question or concern that couldn't be answered by one of these three. Add in Colleen Patrick-Goudreau's Vegetarian Food for Thought podcasts (they make me SO excited to be doing this!) and I would say all of my bases are covered.
Vegan: The New Ethics of Eating by Erik Marcus was a great first stop. It provided an overview of factory farming and the dairy industry, but it's greatest strength was definitely it's description of how veganism can improve your health. Even if I didn't care at all about killing animals (which I obviously do), this book would've given me enough information to convince me to try out veganism. I also rely on the author's Vegan.com website, which is a portal for all things vegan, and yesterday he commented on my blog (!!!!!) about his 21-day kickstart podcasts, which I started listening to as soon as I got home from work.
If you have a question about nutrition and veganism, this book has the answer. Becoming Vegan by Brenda Davis and Vesanto Melina will help you make sure you are getting adequate nutrition through well-balanced meals.
And then there is The Vegan Sourcebook by Joanne Stepaniak. This resource of all resources has the history of veganism, how to live with non-vegans, nutrition information and some recipes. This book really helped me get a better grasp of the vegan lifestyle overall.