The books are a must read for anybody with an interest in animal welfare. The 1st book is as relevant today as the day it was first published in 1975:

Animal Liberation: The Definitive Classic of the Animal Welfare Movement

Since its original publication in 1975, this ground-breaking work has awakened millions of people to the existence of “speciesism”—our systematic disregard of nonhuman animals—inspiring a worldwide movement to transform our attitudes to animals and eliminate the cruelty we inflict on them.

In Animal Liberation, author Peter Singer exposes the chilling realities of today’s “factory farms” and product-testing procedures—destroying the spurious justifications behind them, and offering alternatives to what has become a profound environmental and social as well as moral issue. An important and persuasive appeal to conscience, fairness, decency, and justice, it is essential reading for the supporter and the skeptic alike.

and one of the follow up publications published in 2005 :

In Defense of Animals: The Second Wave

Bringing together new essays by philosophers and activists, In Defense of Animals: The Second Wave highlights the new challenges facing the animal rights movement.

Exciting new collection edited by controversial philosopher Peter Singer, who made animal rights into an international concern when he first published In Defence of Animals and Animal Liberation over thirty years ago

Essays explore new ways of measuring animal suffering, reassess the question of personhood, and draw highlight tales of effective advocacy

Lays out “Ten Tips for Activists”, taking the reader beyond ethical theory and into the day-to-day campaigns for animal rights

And a new kid on the block, an activist writer providing an insight in the attitude towards animal activists and the issues at stake in the USA:

Green is the New Red: An Insider’s Account of a Social Movement Under Siege

At a time when everyone is going green, most people are unaware that the FBI is using anti-terrorism resources to target environmentalists. Here is a guided tour into an underground world of radical activism and an introduction to the shadowy figures behind the headlines. But here also is the story of how everyday people are prevented from speaking up for what they believe in. Like the Red Scare, this “Green Scare” is about fear and intimidation, and Will Potter outlines the political, legal, and public relations strategies that threaten even acts of nonviolent civil disobedience with the label of “eco-terrorism.