As the previous commenter indicated, scale — it’s not physically possible for a human to read that many books.

Even the most dedicated readers will only read a few thousand books in their lifetime. https://www.mentalfloss.com/article/93594/heres-how-many-boo...

ChatGPT is trained on orders of magnitude more books than a human can consume.

https://torrentfreak.com/authors-accuse-openai-of-using-pira...

> OpenAI hasn’t disclosed the datasets that ChatGPT is trained on, but in an older paper two databases are referenced; “Books1” and “Books2”. The first one contains roughly 63,000 titles and the latter around 294,000 titles