The Business of Publishing

The three-category ceiling is now a hard limit with no workaround.

For years, authors were advised to request additional Amazon categories through KDP support, with the understanding that up to ten categories were available if you knew to ask. That system no longer exists. Amazon has eliminated the extended category request process entirely. The KDP support email address that authors were directed to use no longer accepts incoming mail, and the contact form routes through a chatbot that cannot action category expansion requests. You have three category slots. That is the full allocation. Any publishing resource still advising you to request more is working from outdated information.

KDP Select enrollment is opt-in, not opt-out.

When you create a new title in KDP, the KDP Select enrollment checkbox is checked by default. If you do not manually uncheck it during initial setup, your ebook is enrolled in a 90-day exclusivity window before you realize what has happened. KDP Select restricts your ebook from appearing on any competing retail or subscription platform for the duration of that window. The practical consequence is that authors who intend to publish wide from day one find themselves locked into Amazon exclusivity because the interface assumed they wanted to enroll. Uncheck that box intentionally during title creation. Reversing it after the fact requires waiting out the full enrollment period.

Your ISBN choice has distribution consequences most authors do not anticipate.

KDP will assign a free ISBN to your paperback if you do not supply one. That ISBN is tied to KDP and cannot be transferred to another platform. If you later want your paperback distributed through IngramSpark using the same ISBN, you cannot — the KDP-assigned number belongs to Amazon's ecosystem. Authors who purchase their own ISBN through a registry such as Bowker and supply it at the time of KDP submission retain ownership of that identifier and can use it across platforms. The distinction seems administrative until the moment it matters, at which point it is not correctable without creating a new listing.

KDP Select exclusivity does not prevent library distribution.

The widely held assumption is that KDP Select means your ebook is locked out of every channel except Amazon for 90 days. As of a policy change Amazon made in September 2025, that assumption is no longer accurate. Library distribution is now a permitted exception to the KDP Select exclusivity rule. While your ebook remains restricted from retail competitors and subscription platforms, it can now be distributed to library systems through aggregators such as Draft2Digital without violating your enrollment or costing you a single Kindle Unlimited page read.

The library platforms reachable through this exception include OverDrive, Hoopla, BorrowBox, cloudLibrary, and Vivlio Libraries — which covers library systems across France, Belgium, Switzerland, Germany, and Austria. The one operational requirement is that when setting up library distribution, you must select library channels only. Any selection of retail or subscription channels would constitute an actual exclusivity violation.

Library royalties are growing faster than most retail channels.

Aggregated data from Draft2Digital for the January through April window comparing 2025 to 2026 shows library royalties growing roughly six times faster than their retail and subscription partners — approximately 24% year over year. Science fiction is specifically identified as one of the genres leaning into library distribution most aggressively. The shift toward one-copy, one-user lending models has roughly doubled the per-borrow royalty value compared to the previous year. Authors who are currently enrolled in KDP Select and unaware of this exception are leaving an expanding revenue channel entirely untouched.

A cover file built for KDP cannot be submitted to IngramSpark without recalculation.

The two platforms calculate spine width differently, which means the dimensions of a print cover prepared for KDP will be incorrect for IngramSpark even if the page count and trim size are identical. Submitting a KDP cover file to IngramSpark will produce a rejection or a visually incorrect result. Each platform requires its own cover file built from that platform's specific template calculator. Authors who discover this after the fact and attempt to reuse existing files spend significant time troubleshooting problems that are not fixable without rebuilding the cover from the correct specifications.

IngramSpark provides meaningfully better access to library and bookstore wholesale channels.

KDP Print offers an extended distribution option that places your print book in non-Amazon channels, but the wholesale terms and retailer relationships available through IngramSpark are generally considered superior for reaching independent bookstores, library systems, and international distribution. IngramSpark titles flow through Ingram's wholesale network, which is the primary distributor relationship that brick-and-mortar booksellers and library acquisition systems use. If physical retail presence and library availability matter to your distribution strategy, IngramSpark is the more effective tool for that purpose. Using both platforms simultaneously for print is possible, but the cover file incompatibility means the work must be done twice.

Font embedding errors in IngramSpark PDFs are best resolved through Ghostscript.

IngramSpark's file validation process will flag PDFs that contain fonts which are not fully embedded in the document. The instinct for most authors is to return to the source document, make adjustments, and re-export. In practice, re-exporting from the source frequently does not resolve the underlying embedding issue and produces the same error on resubmission. The more reliable fix is processing the existing PDF through Ghostscript — a free, command-line tool that can force full font embedding during a PDF conversion pass. This approach resolves embedding errors that source-document reconversion does not, and it preserves the visual integrity of the formatted file.

Why your ISBN might not show up where readers search.

When your book is assigned an ISBN, there's an expectation that it becomes findable — searchable by readers, retailers, and cataloging systems. In practice, that visibility isn't instant.

Public ISBN databases (isbndb.com among them) once updated within a week or two of a new registration. The current volume of independently published books has stretched that window — in some cases to several months — before a newly registered ISBN appears in search. If your book isn't showing up when you search your own ISBN, that's very likely the explanation, not an error in your registration.

Most of these databases offer a manual submission option, where you can enter your ISBN directly rather than waiting for it to be picked up passively. Submitting manually can bring your book into the database within days instead of months. This is a structural lag in how these databases work, not something specific to any one publisher or platform — worth checking regardless of where or how recently you published.