The Book Industry Study Group (BISG) has led the industry approach to expanding ISBNs from 10 to 13 digits. The BISG has made available a special site which provides a comprehensive overview of the new 13-digit ISBN--why it is necessary, how and when to get ready, etc.
The introduction provided by this website follows: The ISBN provides a standard way to identify books in global trade. In 2007, the publishing industry began using 13-digit ISBNs, phasing out the use of 10-digit ISBNs. This change affected everyone who uses ISBNs throughout the world.