Shoulders by Boyer Coe is an excellent ebook on Boyer's approach to shoulder training.
Boyer details the anatomy and function of the different shoulder muscles including the deltoids and trapezius muscles, and also talks about the interconnectedness of it to the back and chest.
Boyer also describes the many exercises that he utilises, as well as the particular way that he executes them, which is different to other bodybuilders of the golden era. As an inventor, he also describes the different machines that he invented to target his shoulders better.
He also describes several programs that can be used for beginners, intermediate and advanced lifters. 16 pages