I have this book, but not at my current house, so I will give you an impression from my foggy memory.
The pictures are very pretty, but in my opinion they are not very useful as a reference. The soldiers featured in the pictures seem to be selected randomly, so it is difficult to learn about the uniform details in a methodical way. For example, I like to know what officers, soldiers, and musicians of a single unit looked like from a specific campaign; this book will not give you much information.
However, I think the
text contains useful information about facing colors, organization, uniform evolution etc, but hopefully someone with a copy can confirm this.
I prefer a more focused but detailed approach. For example, for my 1809 French army, I used "The Napoleonic Sourcebook" for general uniform information, and "Napoleon's Soldiers" for the uniforms of specific units and ranks. The first is pretty dense and boring, and google images will work just as well as the latter.
There is some good info in this thread as well (
viewtopic.php?f=12&t=4823&p=64325&hilit=Uniforms+of+the+Napoleonic+Wars#p64325) even including some recommendations for the book in question.
So in the end, it depends on your purpose. It would make a nice "coffee table book" and could inspire your painting, but I think there are better resources in terms of depth.