There were a few possible reasons why the books in the novel bookshelf could sometimes be opened and sometimes not: 1. Network problems: If the network is unstable or malfunctioning, it may cause delays in reading progress or the inability to open all books. You can try to restart the computer or reconnect to the network to ensure that the network connection is normal. 2. Bookshelf system update: Some bookshelves may be updated, causing the books in the bookshelves to become unusable. In this case, he had to wait for the system update to complete before trying to open the book. 3. Bookshelf resource problem: Sometimes, the resources in the bookshelf may malfunction or be damaged, causing the books to be unable to be opened. You can try to find the same type of books on other websites or use other reading software to read. 4. Bookshelf version problems: Some bookshelves may have version problems that cause books to be unable to be opened or delay reading progress. You can try upgrading the bookshelf system or use other bookshelves to read. If the above methods cannot solve the problem, it is recommended to contact the customer service of the novel website or the support team of the reading software for help.