Now, I know this is a mainly a food-y blog rather than a book-y blog, but this book deserves a special mention. It's called The Year Of The Flood, and it is by Margaret Atwood. It has a number of themes that will appeal to vegan/eco people, and is also seriously good.
Set in the near future, the book follows a group of 'God's Gardeners' through the mysterious 'waterless flood', and tells of their journey and history. The book is gritty, funny, tender, shocking, compulsively readable. Atwood's characters are as complex as her themes and subject matter are expansive. Covering ecological and humanitarian disaster, this book is extremely relevant and bang up to date.
It follows Atwood's earlier book 'Oryx and Crake' (which I loved!) and expands on alot of the ideas it contained.
I'm not much of a reviewer, I know, but check out the website for a feel of it http://www.yearoftheflood.com/ . The website is full of resources and information on a number of broadly 'green' topics, and very interesting.