Swimming constitutes a "complete" workout in itself, not just in terms of the muscles, respiratory and cardiovascular system, but also in terms of functionality: diving, rescuing, swimming, transporting, etc.
While I've only been swimming for a few month's, I really found reading this book both enjoyable and helpful.
The swim stroke techniques may be a bit outdated but there's definitely some solid principles in here. And it covers not only the techniques of it's time but also water survival and rescue.
The book is illustrated with actual photos throughout. Some are taken on dry land with the person in the photo lying horizontally on a short stool. Showing the swim positions you'd execute while in the water. (Currently working on one known as The Mariner). Others show diving, water rescue, and procedures to follow if you're boat has capsized.
If you're looking for something to help you on a modern competitive level, I'm sure there's better and more comprehensive books out there. But if you like learning about the way thing's we're done in a time long past, you may very well enjoy this.
Of historical interest but otherwise useless. This was before the development of front crawl, back crawl and butterfly strokes. 3 of the 4 main strokes used in swimming today.