Why Nearly Half of Kobo’s Self-Published Books Get Rejected

Rakuten Kobo, a popular self-publishing platform, rejected 45% of book submissions in 2025. That’s almost half of all the books sent to them.

Michael Tamblyn, Kobo’s CEO, explained that most rejections came down to poor-quality AI-generated content. In fact, over 80% of rejected books were clearly created by AI and judged to be very low quality.

Tamblyn emphasized the point: “The 45% is the share of submissions rejected, not the share of submitted books written by AI.” This means not all books use AI, but many low-quality ones get filtered out.

Kobo has strict rules for what they accept. They reject books if titles are too short, if content is AI-generated but poor, if translations are bad, or if prices are too high. They keep the right to refuse or remove any title at any time.

Interestingly, Kobo uses AI themselves to analyze book texts during the review process. This helps them spot AI-generated content and low-quality work more easily.

Unlike Kobo, Amazon’s Kindle Direct Publishing requires authors to declare if their book was written with AI when they upload it. Kobo doesn’t have that rule yet.

Kobo hasn’t shared how many total books they reviewed or broken down the exact reasons for every rejection. But the high rejection rate shows they are serious about quality control, especially against poor AI writing.

The surge in AI-generated books has created new challenges for self-publishing platforms. Many authors use AI tools to write quickly, but not all produce good results. Kobo’s approach aims to keep the marketplace clean and reliable.

This crackdown also raises questions about how AI-generated content should be handled in publishing. Should platforms require disclosure? How do they balance innovation with quality?

For now, Kobo’s strict screening means authors must focus on quality whether they use AI or not. Otherwise, their books might never make it to readers.