I borrowed this book in kindle format from my local library because the price to purchase the kindle version seemed rather high to me ($24+ at Amazon). However, after reading it, I could recommend paying a higher price for the book, especially if you are interested in growing or gathering mushrooms.
I was looking for a general introduction to mushrooms and their myriad uses. This book gave me that and much more. The first part of the book goes into great detail about the amazing uses of mushrooms, from cleaning up toxic waste, to rehabilitating landscapes devastated by fire, over-harvesting, or pests, to cancer prevention, to facilitating the growth of other agricultural products. And oh, by the way, food.
The second part of the book is a manual of how to grow mushrooms and mycelium in various habitats and for various uses. It seemed to be targeted primarily to organizations and governmental entities that might be interested in one or more of the remedial uses of mushrooms, but there was some information that would be useful for the small private grower. I skimmed most of this, since I'm not planning to go into mushroom production. But you should at least skim it to get a flavor of the different ways it can be handled.
The third part of the book is essential a catalog of specific varieties of mushrooms, with much detail about habitat, characteristics, and uses. Again, I skimmed this, but just this section would make the book worth purchasing as a reference.