"ANA Grading Standards", without doubt or hesitation. It's not A good grading book... it's THE good grading book. It's mandatory and indespensible.
It is the best. But in my opinion it is imperative to get them all. You can never learn enough about grading. You'll find additional help here - Coin Grading
He's right you know. With so much going on in coins today, you really need to know what your doing. I know since I'm probably one of the Worlds worst graders of coins.
Another major factor : the ANA Guide is useful for circulated coins - it's the standard. It's almost worthless IMO for mint state coins. I suggest "How to Grade U.S. Coins" by Jim Halperin for mint state coins. It teaches a method applicable to any coin, although one will always need to familiarize themselves with the ins and outs of a given series.
I would agree, because you will learn that all of these grading systems grade differently. And you will find that the TPG's also grade to their own standards. So that is why there will never be complete agreement on what the grade of a coin "really" is.
Another good grading book is "Grading Coins by Photographs" by Q. David Bowers. As other have stated, you cannot have too many grading books. I have almost every one.
Buy it. It is the best one to start out with. In time you might find you want/need others but that's then and not now!
