* No central database: There isn't a single, comprehensive database that tracks every book ever published.
* Different definitions of "book": What constitutes a "book" can vary. Do we include self-published works, academic papers, e-books, or only physical print editions?
* Constantly changing: New books are published every day, and some older works go out of print.
Estimates:
* Some estimates suggest there are over 130 million books in existence.
* Others put the number at well over 100 million.
It's safe to say the number is incredibly vast and constantly growing!