Few subjects have such a reputation for being boring as trigonometry. Most students who study it miss both the historical context and the interesting applications because most textbooks are too dry and skip the story that gives the subject meaning. Eli Maor’s book, Trigonometric Delights, addresses these shortcomings by a offering a historical development of trigonometry that will be eye-opening even to professional mathematicians. It’s not a textbook or a tutorial but an in-depth guide to some of the most important and beautiful theorems and applications of the subject. Having past exposure to trigonometry helps as Trigonometric Delights is not popular mathematics literature intended for casual browsing. The book is ideal for teachers who want to spice up their trigonometry classes with exciting material, and as an added bonus it is completely free online.