I am a plumber and I think that this book is a really good reference book for plumbing students. It contains a lot of information and is very easy to use. It is basically a plumbing dictionary. Everything is in alphabetical order, so you can go straight to what you need to know. Say for example, you want to know what an anti gravity valve is. You look it up and this book will explain what it is and what it does.
But beware, this is only a reference book, you cannot rely on it to explain most plumbing principles, so if you are on a budget and can only afford one book for your studies, you are better off getting something else, like the JTL for example.