What is an ISBN number? 

An ISBN is an International Standard Book Number. Originally, these were 10 digits in length but since 2007 they now consist of 13 digits.
The number identifies the Publisher, the type of book, the geographical region of publishing and from where it can be ordered.

If one is just self-publishing a book to sell copies oneself or through a single outlet such as Amazon, then an ISBN is not actually necessary. However, if you have designs on your book being available to a wider audience then it is essential. Without a valid ISBN, your book will never be available through the normal distribution channels.

For a single ISBN for a self-publishing author, the cost is around £90 and must be purchased through your national agency. It is not possible to buy an ISBN for a different territory.

If an ISBN is purchased, or allocated, by a self-publishing company, such as Amazon, then the coding will clearly identify to the book trade that this is a self-published book and you may find it difficult to get listed in bookshops.

Whilst an ISBN from a Traditional publisher is not going to necessarily secure a position in your local bookshop, it will certainly improve your chances.

Apart from identifying your book, the ISBN can be used to track sales. Nielsen’s keep data on every book in print and on reported sales. This is how best seller charts are created. Nielsen’s will sell data sets to individuals or organisations such as publishers or newspapers. This data can reveal exactly how many copies of a book have been sold and even where. Invaluable information for strategic planning.