ASIN stands for Amazon Standard Identification Number. It is used by Amazon to identify the items available in the shop. Thus, the number is unique for every article. It consists of a combination of 10 letters, numbers or a combination of both. The number can be found on the respective item’s page in the Amazon online shop. When it comes to books, the ASIN number is the same as the ISBN. All numbers of other items are created when it is uploaded to Amazon’s catalog of products. To locate a specific version of an item, the ASIN can be used in Amazon’s search.
Your own e-book is assigned its unique ASIN after you uploaded it to the kindlestore. However, after receiving the ASIN for your e-book, you have to add it to the e-books information before re-uploading it to Amazon or the kindlestore. Thus, when publishing a book in the kindlestore, the ASIN is a great alternative to ISBN. However, ASIN numbers are valid on Amazon only. In contrast, the ISBN number is universally used to identify the same book of the same edition.
Here you can find more information about ASIN and other numbers used by Amazon.