An e-book with a file size of more than 5M usually meant that the book had more than 5 million words or an e-book that contained a lot of pictures, audio, or video content. Such a large e-book file required more storage space. If you can't read such an e-book file, try the following methods: 1 Look for free or open-source e-book readers that might be able to support larger file sizes. Try using smaller e-book readers. These readers may be able to read smaller e-books but may not support all e-book format. If the file size exceeds the storage capacity of your computer, you can try splitting the file into multiple smaller files or use some file compression tools to compress the file. If the file size exceeds your network's limit, you can try to download the file to your local computer and read it again. Please note that some e-books may contain illegal content. If you try to read such e-books, you may violate relevant laws and regulations. Therefore, it is recommended that you abide by the relevant laws and regulations when reading e-books or choose legal e-book resources.