AI now writes most new Amazon ebooks — and readers can tell

Detected AI content in new Kindle releases went from near zero in 2022 to 30% in 2023, 45% in 2024, and past 60% by the end of 2025 — it crossed the halfway mark sometime mid-year. That's from an NBER working paper by Imke Reimers (Cornell) and Joel Waldfogel (University of Minnesota), who ran AI detectors across a sample of roughly 10 million Kindle titles published 2020–2025.

Volume exploded alongside it. Monthly new releases sat near 100,000 through late 2022, then tripled to 300,000+. Some genre pockets are far worse than the average: Originality.ai flagged 77% of Amazon's "Success" self-help subcategory and 82% of "Herbal Remedies" titles as likely AI — including apparently fabricated authors, one of whom shipped 74 books in five months.

The twist is that readers aren't fooled. AI-flagged books draw markedly less engagement and lower adjusted ratings, and the damage concentrates on first-time authors rather than established ones. The paper still scores it a net win for buyers — roughly 7% higher consumer surplus in 2025 — because cheap books are still books.

Why it matters: generation is free now, so discovery is the bottleneck — Amazon's ranking algorithm has quietly become the editor of the world's largest bookstore.