This is a terrible textbook.
The book just throws equations at you without any reference to how they translate to the physics itself. It does not attempt to draw meaningful conclusions from the equations it arrives at. It might as well be a list of equations listed one after another.
The author never really explains why or how the steps taken are relevant, and no attempt is made to explain the topics in a lucid fashion.
For a good example of how to make complex equations and concepts understandable, refer to JD Anderson textbooks.