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Format SpecificationsThe unzipped EPUB files may be divided into three categories: XHTML documents, packaging files and container files. XHTML Documents. XHTML is a strict version of HTML. The stricter syntax enables reading systems to render documents more easily. This was important for devices with limited computing power. However, modern tablets and smartphones can all read regular HTML. Packaging Files. They include two files: one with the .opf extension and another with the .ncx extension. The .opf file contains book information (author, publisher, etc.) and a list of all files in the book package. The .ncx file tells the sequence and organization (parts, chapters or sections) of XHTML documents in a book. Container Files. They must be placed in a folder named "META-INF". These files are used for encryption and digital rights management (DRM). For an eBook without DRM, the container file has only a few standard lines. EPUB Viewers (Readers)Traditional EPUB viewers did not take advantage of the browser's power. Another disadvantage is that they are the applications subject to Apple's 30%-cut rule: Apple will charge 30% of the list price for each book sold through in-apps. To by-pass this rule, more and more companies are developing Web-based viewers such as Amazon's Cloud Reader. In September 2010, we released the first offline Web-based ebook viewer for our proprietary format. The Web EPUB Viewer was released in July 2011. Two months later, the Web Books Viewer that can read both EPUB and Web formats was developed. It works on a wide range of computers and mobile devices, including Apple's iPad, iPhone and iPod Touch, as well as Android-powered smartphones and tablets. For laptops, the Viewer works on FireFox, Chrome and Safari. Next year, it will also work on IE 10. The Web Books Viewer uses many new features in HTML5, which is not fully implemented in most browsers yet. In the near future, as browsers in both laptops and mobile devices become more powerful, the superiority of the Web-based viewers will become more obvious. Free EPUB BooksGoogle has more than one million public domain titles in the EPUB format and Project Gutenberg has over 30,000 titles. Ebook Center is improving the quality of the EPUB books at Project Gutenberg, where the Table of Contents were generated automatically and not accurate. Creating EPUB BooksYou may use our online tool to convert Word into EPUB.
Frank Lee |