This is the 1686th most frequent German word.
bücher
Books.
Here, 'Bücher' is used as a plural noun, referring to physical books in general.
Ich lese gerne alte Bücher.
I enjoy reading old books.
In this sentence, 'Bücher' is again a plural noun, indicating various texts available in a library.
Die Bibliothek hat viele spannende Bücher.
The library has many exciting books.
Here, 'Bücher' represents specific course-related books, used in a questioning context.