There are many books that directly or indirectly address the subject of veganism and animal welfare. Here are just a few (more to come):
Eat Like You Care – An Examination of the Morality of Eating Animals
Gary L Francione & Anna Charlton (it’s from this book that I have the figure of 57 billion)
Mind if I Order the Cheeseburger? – And Other Questions People Ask Vegans
Sherry F Colb
Both the above books are written by lawyers, and make a very clear and well-reasoned argument. It’s difficult to read them and still be persuaded that eating meat is OK.
The World Peace Diet
Dr Will Tuttle
Animals as Persons: Essays on the Abolition of Animal Exploitation
Gary L Francione
Animals and the Moral Community: Mental Life, Moral Status, and Kinship
Gary Steiner
THE ETHICS OF WHAT WE EAT: Why Our Food Choices Matter
Peter Singer and Jim Mason
Eating Animals
Jonathan Safran Foer
Farmageddon: The True Cost of Cheap Meat
Philip Lymbery
Why We Love Dogs, Eat Pigs, and Wear Cows: An Introduction to Carnism
Melanie Joy
The PETA Practical Guide to Animal Rights
Ingrid Newkirk
Beasts – what animals can teach us about the origins of good and evil
Jeffrey Moussaieff Mason
The Pig Who Sang To The Moon
Jeffrey Mason
The Vegan Cook & Gardener: Growing, Storing and Cooking Delicious Healthy Food all Year Round
Piers Warren and Ella Bee Glendining
https://shop.permaculture.co.uk/the-vegan-cook-and-gardener.html
Ecological Ethics
Patrick Curry
In-depth exploration of the many aspects of, loosely, the green movement
Toward a Transpersonal Ecology – developing new foundations for environmentalism
Warwick Fox
Written in 1990, this book is still relevant; it examines our human-centred approach to the world and offers a different perspective