This is a short, critical, morally sound and instructive book. It's teachy, not preachy, and is based on two principles:

1) Humans have a moral obligation not to impose unnecessary suffering on animals. 2) Animals matter morally, but humans matter more.

I, a vegetarian since six years, got angry while reading this book. Angry at myself and at the meat, dairy and egg industry. Some of the findings in this book are details that I already knew, some are daunting and shocking but all are easily found (and verified), for instance that over 100 million male chicks are killed each year, because they are biologically unable to lay eggs, and other information shocked me because I didn't know of it, e.g. the vast amounts of grain that animals are fed in order to eat them or their produce, in relation to how many people can be fed using that very same grain instead - while not leading to the systematic torture of animals, ruin of water sources and our bodies in the process.

The authors make a very stable case for how eating animals and animal products is not equal, morally speaking, to torturing animals for enjoyment; and yes, they actually don't preach as they do this, but use logical arguments that anyone can follow.

A vegan way of life is - naturally - suggested by the authors, who give tips on how to go about this, in an easy and most palatable way.

All in all: short, highly recommendable and natural for all humans.