What's an ISBN?
ISBN is an International Standard Book Number. ISBNs are 10-digit or 13-digit codes used by the publishing industry to uniquely identify individual book titles and editions. Some 10-digit ISBNs may end with an "X" instead of a digit.
ISBN-10 vs. ISBN-13
Effective January 1, 2007, the International Standards Organization (ISO) approved a change from 10-digit to 13-digit ISBNs to alleviate the increasing volume of new books entering the system.
All books published on or after January 1, 2007 will be assigned a 13-digit ISBN. Books published prior to January 1, 2007 will retain the original 10-digit ISBN and be assigned an equivalent 13-digit ISBN code.
The ISBN is most often found above the barcode on the back cover of a book or sometimes on the inside-front cover of newer paperbacks. The ISBN may also be found on the copyright page of the book with the other publishing information and is usually located in the middle of the page.