What is in a book barcode
A book barcode is an EAN-13 that starts with 978 or 979, with "ISBN 978-..." printed above it. Many books add a 5-digit add-on to the right. In the US, it carries the price: 5 for US dollars followed by the amount, so 52495 means $24.95, and 90000 means no price. Korean books use the add-on for a classification code instead.
Where do ISBNs come from?
Each country has an ISBN agency, such as Bowker in the US and Nielsen in the UK. Some agencies issue them free, others charge.