is a good book to start with. The most valued medicinal mushrooms grow on trees
and are consumed in the form of a tea.
This is because most of them are so tough
that it would be easier to eat one's shoe.
If you find them available for purchase, it would most likely be at an herb store
or on line. The best thing is to find a knowledgeable teacher who can show you
where they grow. In places like Southeastern U.S., Chaga is a good one to learn about.