ISBNs: what they are, when to use them and a family legacy I’m grateful for

If you’ve ever looked inside the first few pages of a book, you’ll almost certainly have seen a bar code and a long number beginning with 978. Most readers skim past it and plenty of first-time authors barely give it a thought.

But that number, the ISBN, matters far more than people realise.

So, what is an ISBN?

An ISBN (International Standard Book Number) is a unique identifier for a specific edition of a book. Like a fingerprint for your book.

Every format needs its own ISBN:

• Hardback

• Paperback

• Ebook

• Audiobook

Change the format? New ISBN.

It’s how bookshops, libraries, distributors, and databases know exactly which book they’re dealing with.

KDP ISBNs vs owning your own ISBNs

This is what you need to weigh up as an author.

If you publish through Amazon KDP, Amazon will assign you a free ISBN.

That sounds appealing and may be the right choice. But you should be aware of the potential trade-off.

With a free KDP ISBN:

• Amazon is listed as the publisher

• Your book is tied to Amazon’s ecosystem

• You have limited flexibility elsewhere

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With your own ISBN:

• You (or your imprint) are the publisher of record

• You can distribute wherever you choose

• Your books sit properly in the wider publishing world

For anyone thinking long-term, wanting to access libraries, bookshops, museums, schools or archives, owning your ISBNs gives you control and credibility.

How do you get an ISBN in the UK?

In the UK, ISBNs are issued by Nielsen (specifically Nielsen BookData).

You can:

• Buy a single ISBN

• Or purchase a block (10, 100, or more)

And here’s where a bit of family history comes in.

A publishing decision made in the 1980s — and why it still matters

Back in the 1980s, my grandad purchased a block of 100 ISBNs. This was long before self-publishing platforms existed. At the time, I doubt he imagined just how valuable that decision would become, nor that his own story would be published using one of those ISBNs!

Today, as we publish more family histories, diaries, memoirs, and research-led books under the SynJon imprint, those ISBNs are a real asset:

• They anchor our books as properly published works

• They preserve continuity across generations

• They give us independence and flexibility

It’s one of those quiet, behind-the-scenes choices that pays dividends decades later.

If you are thinking of publishing more than one title, or more than one format then you might want to consider a block purchase of ISBNs.

Legal deposit: the bit many authors don’t know about

In the UK, publishing a book comes with a legal obligation. For every book published, a copy must be sent to the British Library. This is known as legal deposit — and it ensures that every published book becomes part of the national archive.

Other libraries may also request copies, but the British Library deposit is automatic and mandatory.

Separately, your book’s data should also be registered with Nielsen, which feeds into:

• Bookshop ordering systems

• Library catalogues

• Sales and bibliographic databases

It’s how your book becomes findable beyond your own website.

Why this all matters more than you might think

ISBNs aren’t exciting. They’re not creative. They don’t sell books on their own.

But they:

• Protect your authorship

• Support long-term discoverability

• Signal professionalism

• Future-proof your work

Whether you’re publishing one book or many, they’re part of the book publishing process and you’ll need to think about them sooner than you might think!

Sometimes the most important publishing decisions are the quiet, behind the scenes ones or, in my case, the ones made years (or generations) in advance.