The total number of books published in the United States with ISBN numbers has reached a record high in 2025. According to statistics compiled by Bowker and published by Publisher's Weekly , output jumped 32.5% over 2024 levels, totaling more than four million titles.

Self-publishing drives market growth

The industry-wide increase was led by a massive surge in self-published works. The number of self-published print and e-books (including those without BISAC codes) soared 38.7%, rising from 2.5 million in 2024 to more than 3.5 million in 2025.

This performance marks a significant rebound for the sector, which had seen a decline in 2024 compared to 2023. Taking a long-range view from 2022 to 2025, the number of self-published books has jumped 43.5%.

Even though the report does not explicitly state this, the increased use of AI tools is likely to be a key factor in the explosion in self-publishing output. This is why commentators on LinkedIn are warning of a wave of “AI-slop”.

Traditional publishing trends

Traditional publishing also saw growth, though at a steadier pace. A total of 642,242 traditionally published books were released in 2025, a 6.6% increase from the 602,428 titles released in 2024. Over the three-year period beginning in 2022, traditional output has increased by 10%.

Of the traditional titles released in 2025, 310,513 included BISAC codes for category classification. Data suggests that self-published authors are increasingly recognizing the importance of using these codes for book discovery.

Factors behind the rebound

Andrew Kovacs, Product Marketing Manager for Bowker, pointed to the "growing availability and adoption of new tools in the author community" as a primary driver for the 2025 rebound.

“The fact that every aspect of the publishing process once available only through traditional publishers can now be obtained from the self-publishing service providers at a comparable level of quality is likely the key driver in lifting output,” Kovacs stated.

He further noted that these tools assist authors with writing, publishing, distribution, and marketing. Additionally, the ease of publishing the same title across multiple formats—hardcover, paperback, and e-book—contributed to the rise, as each format requires a unique ISBN.

Self-published genres

The vast majority of self-published titles were released as e-books. The top five genres, which together with self-help accounted for over half of the total output increase, were:

• Fiction: 477,104 books

• Juvenile nonfiction: 401,716 books

• Games and activities: 354,684 books

• Juvenile fiction: 265,615 books

• Travel: 246,615 books

Traditional published genres

On the traditional side, adult fiction and juvenile fiction remained the most popular categories, despite both seeing slight declines from 2024 levels:

• Adult fiction: 39,681 books

• Juvenile fiction: 24,768 books

• Juvenile nonfiction: 21,283 books

• Business and economics: 18,105 books

• Religion: 16,095 books