I loved learning trig from this book, back in 1967.
I really learned it, it stuck with me forever, and learning it was more like a game because of the self-teaching approach used in this book. I have never, in 50 years, forgotten any of the basics of right angle trigonometry, a basic skill that has proven necessary in multiple science and engineering work.
The teaching technique is really like "find-your-own-adventure." You read some text, then choose from 2 or 3 answers to a question, and go to the page to either confirm your knowledge or get insight into why you chose wrong. It is a great way to learn.
This was the first book I ever read to teach myself something without a class. Before starting the class where I would learn trigonometry, I pulled this out of the Houston County Library and