The number of books that make a "library" can vary depending on context and perspective, but common benchmarks suggest:

• Around 500 books can make a room start to "feel like a library" in a personal home setting.
• Many consider 1000 books a popular number for defining a library collection.
• The American Library Association suggests around 5000 books to form a collection that really "feels" like a library.
• In smaller or resource-scarce environments, even 500-2000 books can be sufficient to be considered a library.
• Some see a well-curated collection of as few as 25 books as qualifying as a library, focusing on the quality and selection rather than just numbers.

In short, a personal or physical library typically ranges from a few hundred to thousands of books, with 500 to 1000 often seen as a reasonable lower limit for calling a collection a library, but there is no strict universal number.