ISBNs & Distribution

You don't have to buy an ISBN

KDP assigns a free ISBN automatically when you publish, so this isn't a required cost. The tradeoff: a free KDP ISBN lists Amazon as the publisher of record, and it's tied to Amazon specifically, you can't use it to distribute the same edition through other retailers or IngramSpark.

When buying your own makes sense

Buying your own ISBN (through Bowker in the US) lists you as the publisher and lets the same edition go wide, other retailers, libraries, IngramSpark. Bowker sells them in blocks: roughly $125 for one, $295 for a block of 10, and $575 for a block of 100. A single title usually only needs one ISBN per format (ebook, paperback, hardback each need their own), so a block of 10 covers most authors for several formats or a small series without paying the per-book rate of buying one at a time.

Going beyond Amazon

KDP alone only reaches Amazon. Draft2Digital and IngramSpark are the two most commonly used routes to "go wide", ebook and print distribution to other retailers and libraries. Draft2Digital tends to be simpler to start with; IngramSpark has wider library and bookstore reach but a rougher upload process.

KDP allows ebook preorders (up to a year out) but not paperback preorders, the paperback only goes live once you publish it for real.

Kindle Unlimited or wide?

Enrolling in KDP Select puts your ebook exclusively on Amazon for a 90-day term that renews automatically until you opt out, in exchange for two things going wide doesn't give you: Kindle Unlimited page-read royalties, and access to Amazon's own promotional tools (Free Book Promotion days, Countdown Deals). Going wide is the opposite trade, no exclusivity requirement, but no page reads and no KU-specific promos either.

KU tends to work better for a debut author without an existing audience, or in a genre where readers read primarily through Kindle Unlimited (romance, fantasy, and thriller lean heavily KU). Going wide tends to work better once you have your own list or following that can drive direct sales elsewhere, or if reaching readers outside Amazon's markets and libraries matters for your specific book.

Neither choice is permanent. Enrollment renews every 90 days, not forever, so this is something you can revisit each term rather than a one-way door.