I purchased this book, because I found the Nik Software Collection's built-in help to be very perfunctory. The built-in help summarizes what a particular tool does and briefly describes the controls. However, it doesn't always describe what the ramifications of changing those controls do to the photo. That is why I wanted to buy this book. However, the book ends up being a mixed bag.
1) The first chapter covers some aspects of capturing photos and selecting photos to edit in post-processing. I felt that this chapter was unnecessary, because its space could have been used to talk more about the software. There are plenty of other books dedicated to the topic of capturing photos (composition, etc.) and selecting photos. Even this book states that this topic "could fill volumes" (page 3). The book may have been better off providing a short bibliography for such topics.
2) The images that show off the Nik Software interface are too small, as other reviewers have mentioned. For a book about teaching the reader how to use the software, it is essential that the images of the software interface be readable. Not everybody has good vision. In addition, the authors do not highlight parts of the interface when talking about a particular function like other photography software books. For example, the author would talk about a function and then refer to Figure X.Y. When you go look at Figure X.Y, it's hard to tell what in the interface has changed. The book should circle the area in question, use a callout, or some similar technique.
3) My main interest was in learning about all of Color Efex Pro 4's controls. On page 144, it says "With 55 filters and a pretty good online help system, we won't go into what each slider does in this book." Unfortunately, most people buy these books, because the online help is bad! Software vendors have spent so little money and effort on their instruction manuals that customers have become accustomed to them being bad.
To be fair, I did check out Color Efex Pro 4's online help. It shows you an HTML version of the interface with hot points that you can click to bring up help for it. The content in the online help describes what the controls do, but it is still basic. For example, when I checked out the Global Contrast control for the Bleach Bypass filter, the online help says, "Controls the overall contrast of the image." That is somewhat of a "captain obvious" description, and something I have come to expect from an online help system or software manual. This is why I would have expected this book to delve further on topics like that, but the book does not sadly.
4) The book's writing is very good. The writing is not too dry and also does not try to get too funny like some of Scott Kelby's books.
In conclusion, I can't but feel that this book should have been the software manual. The biggest letdown is the Color Efex Pro 4 section, since it does not cover every control of every filter. I suspect another author will be publishing a book about this, to which people will have to pay again. :-(
When the software maker publishes a book about their own software, I expect it to be comprehensive and go beyond the software manual or online help. This book isn't there yet.