A study analyzing over 14,000 self-published e-books on Amazon reveals that AI-generated content is expanding the platform’s book catalog by 38.3 times since early 2023, yet total revenue growth has only reached 8.9 times during the same period, creating a dilution effect as more books compete for limited income. Even non-AI books saw declining earnings in most genres, though they still generate 72.5% of overall revenue. AI books make up 20% of the catalog but account for only 12.1% of sales and 11.3% of revenue, yet their share in bestseller lists has risen to 31%. Some authors rely heavily on AI to increase output and earn millions from a few works, with these books showing high linguistic overlap with existing published content. Industry experts say the findings provide evidence useful for future AI copyright lawsuits, potentially influencing rulings on fair use as companies previously argued human input justified their use of AI.