1.
archive room; library stacks; book storage
A room or building used for storing books, documents, or archives. In libraries, refers to the closed stacks where books are kept but not openly browsable.
Usage
書庫 can refer to the closed stacks in a library (where books are stored but not freely accessible to the public) or more generally to any room or building dedicated to storing books and documents.
Forms
書 (book, document) + 庫 (storehouse).