The International Standard Book Number (ISBN) records all the information about your book required to buy and sell it. The 13 digit number is calculated mathematically with the last digit being a precise check on its validity. After the standard prefix, it identifies the country and language of the book, followed by the publisher and the format. It is not a legal requirement in the UK but without it the book cannot be ordered through normal trade channels.
You can have a free one through such online publisher/retailers as Amazon. Or you can buy one from Nielson UK at £93. Each. Buying in bulk brings the price down: ten will cost £174. If a book is published in paperback, hardback and ebook, you need one ISBN for each format. Traditional publishers buy them in bulk and allocate them accordingly at no cost to the author. Tweedlecoate does the same as part of the publishing package.
Only books with a Nielsen ISBN can be registered with the major book wholesalers such as Gardners. Book retailers often only obtain their stock from wholesalers such as Gardners. They are most unlikely to order from Amazon because they have to pay full retail price which means there is no profit for them. Wholesalers give them a discount so they can make a profit. This discount is set by the publisher and ranges from 35-40% from a small publisher to the 60% demanded by Waterstones. Tweedlecoate negotiate the discount with each of our authors on each book before setting it with the wholesalers.
Registering with PLR (Public Library Registration) can be done using a free ISBN from Amazon. But if a librarian on a limited budget cannot buy the book form a wholesaler at discount price, they may think twice before stocking the title. Also, they like to see the book in the catalogue first and read robust reviews as opposed to the stars online.
Ultimately, the choice of supplier of the ISBN depends on what you expect from your book. If you are looking for internet sales only with the global reach of sellers such as Amazon, the free one they offer is the obvious one to go for. If you want to see your book in shops and libraries as well, it is worth having a Nielson one. Incidentally, you can register your book on Amazon with a Nielson ISBN and have the best of both worlds. This is the way Tweedlecoate operates. More expensive in the short term but worth it in terms of sales and income streams for the author. For instance, PLR generates up to £6,600 p.a. for a popular author. Tweedlecoate will help you register but all the income is paid directly to you, the author. (see PLR Guide)