The game appears to have 3,072 books to shelve in total, which is the number most sources repeat for Librarian: Tidy Up the Arcane Library!.

Quick scoop

The Steam page says you need to shelve 3,072 books as quickly as you can, and other coverage matches that count.

Variety of books

The books are split into themed sections and series, with titles covering different subjects like monsters, history, jurisprudence, magical artifacts, and more.

In short

If you meant “how many books are there,” the answer is 3,072.