PDR of Herbal Medicine (Physicians Desk Reference) gives herb, dosages, contraindications, studies and is easy to use. It does not go into herbal preparation. I have two books that are my favorite on that:
Paperback; Heinerman's Encyclopedia of Healing Herbs and Spices (lots of good recipes)
Hardback: Encyclopedia of Medicinal Plants: George D. Pamploma-Roger, MD (Expensive but worth it, origins 7th Day Adventists, but the info is right on and in my comprehensive library cross referenced with no errors)