You need to import the directory on Apple's mobile phone before you can display the epub file.

EPub is the abbreviation of electronic publication, which means electronic publication. It is a free and open standard, which belongs to a kind of content that can be "automatically rearranged", that is, text content can be displayed in the most appropriate way according to the characteristics of reading equipment. Use XHTML or DTBook (an XML standard proposed by Daisy Consortium) to display the text inside the EPub file, and the file content is packaged in zip compressed format.