I agree with the other posters.
First, get yourself a copy of
A Guide Book of United States Coins, K. Bressett, Editor; Whitman Publishing. This is "The Rd Book". It provides some very good general information about
US coins.
Then, get yourself a copy of
Strike It Rich With Pocket Change, Ken Potter and Brian Allen, published by Krause Publications. It will give you more specific information on errors.
Both of these books are inexpensive, and can be found either on-line or at your local bookstore.
Also try the
Cherrypickers' Guide to Rare Die Varieties of United States Coins, (Bill Fivaz, J. T. stanton, also from Whitman Publishing). there are two volumes, choose the one that matches the coins you are searching. A little more expensive than the other two books.