Electronic Publication (ePub) is an Open eBook file format and is supported by many e-readers, and compatible software is available for most smartphones, tablets, and computers. Since EPUB files are structured like ZIP files, you can rename an EPUB eBook, replacing .epub with .zip, and then open the file with your favorite file compression program, like the free 7-Zip tool. Inside you should find the contents of the EPUB eBook in HTML format, as well as the images and styles used to create the EPUB file.