For the magical part of your equation, yes. It is a very good book to have. I still refer to it, myself.
Now for the medicinal part, there are hundreds of good books, and hundreds of not-so-good books. You simply have to try one out, I can give you a place to start though:
The Green Pharmacy - James A. Duke
From there, if you type the book to a book store search engine or an online shopping source there will be many good recommendations - I recommend trying out a book before you buy it and see if you can find some books on medicinal herbal applications in a local store. Of course, it helps to work with what you got, and amazon is not a bad place to buy books.
I hope I have helped you in some way.