Sometimes it's hard to write a review because the author's style is so grating that even though he has a lot of useful information, you dislike the book and wonder if you can be fair. After thinking about this book for some time, I think I can be fair.
Engh's basic point is that a photographer who wants to make money with his photographs will sell from stock to markets that are not competitive. He then tells the aspiring stock photographer how to determine what those markets are, how to find the photo buyers in those markets and how to deal with those buyers to get your stock photographs sold. Although I'm not a stock photographer most of the steps he advises have a ring of truth to them and agree with what the stock photographers I know tell me.
But if you are interested in "landscapes, birds, scenics, insects, plants, wildflowers, major pro sports, silhouettes, experimental photography, artistic subjects, (such as the "art" photography in photography magazines), abstracts (such as those seen in photo-art magazines and salons), popular travel spots, monuments, landmarks, historic sites, [and] cute animals" Engh says forget about them. Well, maybe that's too strong. He says when you put those areas on the back burner, "you'll stop wasting time, film, postage, and materials." When I came to this advice, I almost put the book down, because it was clear that Engh wasn't talking to me. Most people take photographs because they are interested in some subject matter or approach and not just to make money.
I also was disturbed by how often in the book the author shilled for his company and web-site, where, he says, useful information is available. It may be, but it appears it's always for a price.
In summary, if all you want to do is make money with your camera, without joy or pleasure, this book may be for you.