This book is all about fish. Their evolution, biology, habitat, food sources, reproductive strategies, parenting methods, schooling behavior, migration routes, etc. Even just the basics about how they sense the world around them and navigate was interesting. The diversity of fish life in the world is really astounding, and the book just touches on some of the many different species, but I think does a good job at highlighting the wide variety of forms fishes have adapted, and different means by which they make their living in the water. Yes it's an old, outdated book but the pictures are pretty good for their age, and I learned a lot of facts. For example, about the heart structure. All these years of reading about animal life, why did it always escape my attention that fish have a two-chambered heart, most reptiles and amphibians a three-chambered heart, and that of mammals and birds, four chambers. This makes sense, but I never thought about it before. The last few chapters describe some then-new scientific studies that tracked where fish go in the ocean, using a variety of tagging devices in the hopes that fishermen, sportsmen and others would return them when found. Even though the return rate was less than 5 percent, they put so many tags on fishes it still generated useful information. There's also a chapter that discusses how the fishing industry was beginning to a see decline in stock numbers, and strategies to remedy that (interesting look at how it was managed in different countries, which I'm sure is all very different now).