Dr. Morton Walker wrote the Olive Leaf extract book and sells for $5.95. This is the only modern book I approve and push for everyone to read. Olive Leaf is the King of all herbs past, present and future! It takes a large book to discuss this herb.
It is harmless, less toxic than drinking water according to the FDA, yet is a powerful herbal medicine. I think it needs to be taken 6 days a week for life and if a health problem arrises, then you take 20 X your daily amount and normally 1-2 days the problem is gone. I use it in just about everything herbally speaking.
This also has to be one of the most abundant herbs on earth and one reason why the herbal books rarely mention it, they want to sell rare herbs that cost you $$$$$. I say pick your own when you can, if not, find someone with a tree and have them send you some leaves.
The BAREFOOT Herbalist