How should we treat non-human animals? In this immensely powerful and influential book, Peter Singer addresses this simple question with trenchant, dispassionate reasoning. Accompanied by the disturbing evidence of factory farms and laboratories, his answers triggered the birth of the animal rights movement. In the decades since this landmark classic first appeared, some public attitudes to animals may have changed but our continued abuse of animals in factory farms and as tools for research shows that the underlying ideas Singer exposes as ethically indefensible are still dominating the way we treat animals. As Yuval Noah Harari's brilliantly argued preface makes clear, this book is as relevant now as the day it was written.