Are you looking for the magical properties or medicinal? I can suggest a few good books that could help get you started.
Books on Herb Magic:
Cunningham's encyclopedia of magical herbs - Written by Scott Cunningham.
Herb Magic for Beginners:Down-To-Earth Enchantments - Written by Ellen Dugna.
Books on Herbal Remedies:
The Book of Herbal Wisdom: Using Plants as Medicines - Written By Matthew Wood
Homemade Health: Home remedies your grandmother knew - Simple & effective treatments from the pantry (Herbology At Home) - Written by Anke Bialas