EPUB, short for Electronic Publication, is an open e-book standard accessible by most of the e-book readers. It has some characteristics that makes it perfect for ebook readers like having a reflowable content (it can adapt itself to any screen). It also has the option to use DRM to sell books and presents a single and elegant document written in Markup Language. It accepts images (as well as vector images) but not video or audio. It has embedded metada and CSS styling. It should became the standard for e-book readers like the html is from web.

The Kindle Issue

The Kindle is heading to became one of the most important ebook readers competing heavily with iPad, iPhones and other devices. The problem is that Kindle doesn't accept EPUB formats. Its true that is possible to make conversion of EPUB format to the Mobipocket format that Kindle can read (for example trough Calibre), and even to have a small app in your Kindle to do it for you (according to Gizmodo). Amazon also offers the service to convert the documents but that means always another step before having your book available. I think if Kindle wants to become the most important reader they have to start accepting EPUB formats.

EPUB structure

The EPUB structure consists in one file that is a zip compressed collection of different files. All of them are needed for the book. You can use any program to uncompress a ebook and see its components.

mimetype: This is the information about what kind of file this is and the formats involved.

META-INF/ This is the folder where all the metadata of the books is located.

• container.xml This XML file points to the file defining the contents of the book, basically the .OPF file..
• rights.html An EPUB file can optionally contain DRM as an additional layer, but it is not required by the specifications. In any case this is the file where all the informations should go.

OPS/ In this folder are where all the files for the book, the chapters, images and metadata.

• book.opf This file explains how all the components of the book works together, and also has all the metadata information. It has three child elements metadata, manifest (all the files in the package), spine (all the XHTML content documents in their linear reading order.).
• chapter1.xhtml All the text in the book is formatted with xhtml (almost like a webpage), and it can be separated in sections for better reading.
• chapter-1-picture.png EPUB accepts PNG, JPG, GIF and other formats normally used in web.

CSS/ This is the folder where the format of the book is defined using CSS”

style.css This is a basic CSS format

myfont.otf Is possible to embed fonts into the documents.

How to create an EPUB document

There are several ways to do it. For example is possible to make it as a HTML document and let programs like Calibre to transform automatically to EPUB. This software also transforms from txt, rtf and other formats. But if you want to create (or edit) an EPUB document from scratch the best way is to use a software specific for this.

There are many apps to create EPUBs, some can be really expensive, Adobe Indesign can create them for example. There are others that can turn your Open Office in a EPUB creator like eScape and is possible to make it by hand using just a text editor. There are also free and open source tools like Sigil.

Sigil

This is an open source software with GNU license that can create EPUB files. Is a multiplataform WYSIWYG editor and creator and is really good to understand how an ebook works. The software works for Linux, Mac and Windows, and although it has some bugs and deficiencies is still growing.

According to the tutorial of Sigil, creating a EPUB book has severak steps. From those, only the first one is required but the other ones (meta data, cover image, sections and table of contents are highly recommended).

• Convert text or html to EPUB format: The best formats to start are txt or html, the later will support some formatting like the headings, bolds and italics. Or you just can paste it (alotugh is not recommended). After this file is created you can edit and add some basic format that will be recorded in the CSS file. Save the new file as an EPUB book.
• Set the Meta Data: In the menu Tools/ Meta Editor, you can add the basic meta data information, and clicking on More you can add much more attributes
• Add a Cover Image: You can add regular images by going to Insert/Image but if you wan to have it as a Cover Image you have to select the image in the Images folder in the right column and with the right click go to Add Semantics and select Cover Image. The image should be JPG, PNG or GIF and works better with 590 pixels wide x 750 pixels high.
• Create Sections: Clicking on Chapter Break to create a new xhtml document, and it works to create pages specifically for the Cover Image, the Copyright notice and other information. This section is not needed for Chapters, because those can be referenced in the Table of Contents.
• Create a Table of Contents: The table of contents is based in the Headings of your document. You can have two options to do this: the document imported from html may already have this headings or you can add a headings directly with Sigil. After the Headings are created you can review in the TOC editor under Tools and select which one you don't want to appear in the Table of Contents.
• Finally you can save it as a EPUB file and it will compress all the information automatically. After that you can send it to your ebook reader.

Sigil has more options, it let you see the code of your xhtml documents and proof read your books. It still lacks a lot of characteristics but the software has a lot of people working on them.

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