Circulated Kennedy Half Dollars

The ANA Grading Standards for US coins does get into the MS grades. It is not real extensive but it does have it. Photograde, as mentioned, is a great book for anything below MS grades. Another good book to have is PCGS' Coin Grading and Counterfeit Detection book. Anything else beyond these are usually specialized type books for one particular coin and they are pricey. I bought one on Franklin half dollars, not a cheap book but I can't wait until it gets here. Some cost more than others, depends on how deep you want to get into collecting. I can't stop myself. It is a really great hobby with alot of great people.