This book is more of digital manipulation than digital painting. The difference is, here, most of the lessons start with a photo, and then proceed on to turn that into a painting of a certain style, be it watercolour or oil.
If you want to learn to paint by eye, just like a non-digital artist, this book is not for you. It doesn't teach you how to create a colour palette from life, instead it teaches you how to create a colour palette from a photograph. Yes, you can then use that as a reference but the lessons are really on replicating, not creating.
Some of the effects are nice so you could still pick up a few interesting tips. But ultimately, this book is more suitable for those who want to work on photos, or have something to work with in the first place.
The software covered are Photoshop and Painter.
(There are more pictures of the book on my blog. Just visit my Amazon profile for the link.)