I imagine I'm like a lot of other people attracted to green technology and saving a bit of money, this book was recommended as a good primer.
It's not very helpful at whichever level you want advice. There is rather a lot of stating the obvious. The science and engineering in it is pretty poor, and the explanations are muddled. Calculating the payback period is important when deciding how much to invest, but this is poorly covered. There is little practical advice on system vendors, or if it's DIY, getting hold of parts, assembling a system and the "gotchas" to look out for.
After reading it I was not confident that I could scope a system for my house, or know the best place to buy, or get the bits to build one. And I'm an engineer by profession. As a guidebook it falls rather short of the mark. Perhaps a subsequent edition could be more rigorously reviewed and edited?