“ISBN” stands for “International Standard Book Number.” It is a unique, 13-digit number (10 digits when assigned before 2007) that identifies your title, like a “Social Security Number for your book”. The number allows for a more efficient mode of marketing and purchasing for retailers, libraries, universities, distributors and individual consumers. In other words: ISBN numbers help our partners identify your book / eBook in the marketplace and report sales accordingly. The numbers are not mandatory with Amazon, Barnes & Noble, Google and many other eBook retailers but required if you want to offer your book in the iBookstore. While ISBN numbers are free in many countries, that’s not the case in the US, where they have to be purchased at Bowker. We are buying them in bulk for our authors and offer them at a discounted rate of $25. If you purchase a single ISBN number at Bowker, it is $125. If you want to offer your book in the print and in the eBook format, please keep in mind that you will need two ISBN numbers. The same applies to foreign language versions of your book. Every language needs a separate number.