A little background: I'm a freelance photographer, not an assistant. I bought this book right after I got out of photography school as a means of learning more about the industry and what potential photography-related jobs might be available to me. What I came to understand is this: if you think being an assistant is a cool part-time job or just something you'll do until you can start making money as a photographer, think again. The most compelling reason to work as a studio assistant is to learn how studio photography works (and doesn't work), and it takes time to do this -- generally years and not months.
Also, if you have no intentions of getting into studio photography, this book may be of limited use to you. While various disciplines are discussed at one point, they are not covered in enough detail to really help you understand what's going on. In short, this book is about helping photographers to set up a scene (either in a studio, a church or an office building) and photograph that scene. Some examples would be fashion photography, weddings, food, products, still lifes, etc.
That said, Proulx gives a wealth of information about what it's like to be on the set of a photo-shoot and generally leaves no stone unturned. You quickly realize that buying a box of doughnuts or cleaning a bathroom sink will be just as much a part of your job as setting up backdrops or strobe lights. It's not glamorous and it's not high-paying, but if you want to learn how a successful studio operates (so that you can run your own one day) there's no better way. Perhaps the most valuable asset this book provides are all the little tips and tricks of the trade...how to negotiate terms of pay, what kind of tape you need, how to keep your tools organized, etc.
However, I find it a little disconcerting that Mr. Proulx cosiders himself as still learning the trade even though he's been doing assitant work for over ten years (if memory serves me correctly). That is not typical I can assure you and I think it is something the author overlooks in terms of his advice to people starting out. The bottom line is, you can learn a lot from being an assistant for a couple of years and it will help you tremendously when setting up your own business, .... It would seem Proulx never made the decision to "take the last step" and start a business of his own.
.... If you're interested in studio photography, get this book.