I am still in the processing of reading, re-reading, and applying what Mr. Shaw wrote in his book--in other words I am not a professional nature photographer...yet! However, I found the information in this book to be extremely informative. He gives great no-nonsense advice about becoming a professional nature photographer. He doesn't give us a pipe dream by saying that it's going to be easy. Like any other business venture, it will take effort to make it work.
Very early in the book he establishes what this book is and what it is not. It IS a description of what has worked for him: publishing his pictures in the printed media. It Is NOT a book that describes the technical aspects how to take great pictures (f-stops, shutter speeds, composition, etc.). He has written a number of other books on those subjects. It is also NOT a book on how to sell your pictures in galleries or how to approach retail buyers about ways to display and sell your pictures in stores.
One of the things I most appreciated was his recommendations about the equipment you will need. He doesn't endorse any particular brand of camera (though it's rather obvious from his captions that he uses mostly Nikon equipment). However, he does give specific advice on the types of lenses you will need and the features that he would look for if buying a camera. He also gives recommendations on the types of filters you might need.
On other (non-camera) items he does, however, give specific name-brand recommendations for such things as tripods, light tables, loupes, slide labels, database software, and other miscellaneous accessories (many of which I hadn't considered before). On most of these, however, he gives multiple recommendations. He even provides a list of manufacturers to contact for more information. I already had a good camera, so I especially appreciated his specific recommendations on accessories. I am quite sure that it has saved me hours of work in looking for and considering what will and will not work.
As mentioned earlier he explains what worked for him: getting his images published in the printed media. His general recommendation for beginning photographers is to first approach (low-circulation) magazines to sell pictures with an article. He gives some very compelling reasons why this is a good idea. He also gives numerous examples of the types of correspondence that you can expect when approaching a potential buyer.
He also explains a little the type of images that photo editors are looking for. (It's unlikely that they'll need another image of a moose, elk, bear, or deer in Yellowstone!)
Another thing that I found helpful was his explanation of his personal filing system. Once again he gives some no-nonsense advice here. His recommendations seem practical but not overly costly. If I have one gripe with the book it's that he doesn't give a complete listing of the categories he uses for his own work. He gives a partial list (which I will probably use as a base) but I wish he would have listed all of his categories. (He indicates in the book that there are roughly thirty.)
Aside from all of the above he has some WONDERFUL photographs in the book. Most of the photos are there without being referenced in the text, but just looking at them inspires me to want to become a better photographer.