There are several synonyms for the phrase 'book collections'. A popular term is 'library' which refers to a collection of books, magazines, newspapers, and other reading materials. Another synonym is 'bookshelf' which specifically refers to a group or set of books displayed on a shelf. 'Catalogue' or 'catalog' can also be used, which refers to a list or inventory of books that can be searched or browsed through. 'Compilation' or 'anthology' can also be used to describe collections of stories or poems in a single book. Lastly, 'archive' can be used to refer to a collection of books that is preserved for historical or research purposes.