I first read Practical Ethics twenty-five years ago, and have re-read it, including the later expanded edition, several times. It is an amazing book, because it quietly, calmly and rationally tears apart most of our conventional views about what is right and wrong, particularly in the areas of abortion, euthanasia, our treatment of animals, how we should respond to global poverty and what responsibility we have towards future generations. Singer is currently a professor at Harvard, and is probably the world's most influential writer on ethics. Certainly, Practical Ethics is the most important book that I have ever read, and I urge you to read it, too.
Singer does not pre-judge anything: he challenges us to throw away assumptions such as 'all human life is sacred' and he exposes the unjustifiability of many of the conclusions that we imagine follow from the differences between people and other animals. He uses logical argument to make us realise that if we want to be moral, we need to fundamentally change many of our attitudes.
Singer uses detailed scientific facts as well as moral argument to explore how we should behave, and comes to many controversial conclusions. He has been accused, wrongly, of being hostile to the rights of people with disabilities, but in fact he is a persuasive advocate for ending all unfair discrimination, and for valuing the comparable interests of all sentient beings equally, even when those sentient beings are not people.
I do not agree with everything in Practical Ethics (though I suspect that when we disagree, it is Singer who is right!), but reading it has still managed to change my life in many ways. Be prepared for a challenging and wonderfully stimulating read.