You could try "Mythology" just from Edith Hamlin. It will give you myths based on the Norse, Greek, and Roman culture.
Along with that, if you can, I would highly suggest a book by Scott Cunningham. The book, called, "Encyclopedia of Magical Herbs". Is a good choice. It will list the properties, the elements, and how you can apply them.
Most of all, just think it through. You can always Get a regular book on herbs. Just that, is knowledge by, itself.