4 February 2026 · 6 minute read
What an ISBN is, and why whose name it is in matters
A thirteen digit number that decides who is listed as your publisher for the life of the book.
An ISBN is the thirteen digit number that identifies your book to every shop, library and distributor in the world. It is what a bookseller types in to order a copy. Most people we speak to have never heard of it, which is fine, and a few have been quietly signed up to an arrangement they would not have agreed to if anyone had explained it.
How many you need
One per format. A paperback, a hardback and an ebook are three separate numbers, and an audiobook is a fourth. A second edition with substantially changed content needs a new one; a reprint with a typo fixed does not.
What they cost
United States: Bowker, $125 for one, $295 for ten, $575 for a hundred
United Kingdom: Nielsen, sold in blocks, roughly £91 for ten
Canada, Australia and several others: free from the national agency
Buying singles in the US is close to a trap. Ten costs barely twice what one does, and you will need at least three for a single book in three formats.
The part that matters
The ISBN is registered to an entity, and that entity is listed as the publisher of your book everywhere the number appears. If a publishing services company registers it to themselves, they are your publisher of record for the life of that edition.
In practice that means a second edition through a different company needs a new ISBN and loses the reviews and sales history attached to the old one. It means the company controls the metadata: the categories, the description, sometimes the price. And it means that if you fall out with them, the listing does not simply come with you.
The free Amazon one
Amazon KDP offers a free ISBN. It costs nothing and it is not portable: Amazon is listed as the publisher, and you cannot use that number with IngramSpark or any other printer, which shuts you out of bookshops and libraries. If you only ever intend to sell ebooks on Amazon, it is defensible. Otherwise buy your own.
What to do
Buy a block of ten in your own name, or your own company’s name, from your national agency.
Register the title record yourself so the publisher of record is you.
Assign one per format, and keep the list somewhere you will find it in three years.
We include registration in your name in every package, and we say so here rather than only in the contract, because it is the single easiest thing to check about anyone you are considering.
The other two
What it actually costs to publish a book
Every line item, with a real range next to it, and the three costs that usually turn up after you have signed.
Self publishing or traditional: which one is actually for you
Not which is better. Which is better for the specific book you are holding.
Your book
Thirty minutes with an editor, free, and an honest read on whether the book is worth writing and what it would cost.