The dictionary's interpretation of the library is that the library is the institution that collects, organizes, and collects books and materials for people to read and reference. The library has the functions of preserving human cultural heritage, developing information resources, and participating in social education. Among them, the collection of books should be the focus for people to read and reference, so as to spread the culture. This is commonly recognized by the world. However, from different perspectives, some people have questioned the function of the library. Ikeda, a famous collector of ancient books in Japan Izov wrote in his book "Hand-Drawn Travel of Japanese Bookstores": "Classic books acquired by the library are labeled and stored in the bottom of the box. It is rare that there is no chance to show up in front of ordinary people. It can be said to be the black hole of books. ". What is the most accurate understanding of the "black hole" of books? ['Focusing on the various disadvantages of the rare books in ancient books.', "Classical books are cherished, and the library's careful collection is understandable.", 'Libraries must not only preserve human cultural heritage, but also spread the culture.', 'The ancient books in the library are difficult to read by general readers.']