Discover the Values of Your U.S. Stamp Errors
Published in 2010, the full-color 15th Edition of the Scott Catalog of Errors on U.S. Stamps features values for hundreds of U.S. stamp errors – including over 100 new listings since the last publication. This 218-page catalog includes some older stamps being documented for the first time, such as U.S. #407, an imperforate irregular block of the 7¢ 1912 Washington-Franklin issue which was salvaged from printer's waste.
Stamps are organized by the type of major error and include other neat info including known quantities, warnings of fakes, and format variations, conditions and defects. There's also a section on Freaks and Oddities.