I agree with everyone about the Redbook but you might want to get it in the "Limited" Large Print Edition! The Large Print Edition is so much easier to read about and view coins. After that, then I would say your next purchase should be the "ANA Grading Standards For U.S. Coins - 6th Edition" to learn the finer points of coin grading. There are many books on every Series and Denomination of coins minted in the U.S. including many books on Varieties and Errors some of which can also be Series and Denomination specific. These can cost you into the thousands of dollars on the initial purchase and many hundreds of dollars to renew to the newer/revised copies every few years. You really have no big need for any of these other books unless you become a serious Collector/Dealer in coins. Also, there is a lot of information to be found online, so if you have questions on a specific coin, I would advise to start there!
Frank
