Take this book and throw it in a garbage can. Because they are absolutely useless. Each fashion collection and especially high fashion collection has its own style and mood. And the model's job is to express this style and mood and make it as more attractive to public as possible. It is a very important subject.
Some model think that when they work without agent they save money on agent's commission.
When modeling agency negotiating the terms of your job with clients be sure that you will get the highest possible rate. Please understand very important thing. If you want just to fool around and pretend to be a model. Go ahead - be a free lancer. If you don't work, they make nothing.