EPUB, short for electronic publication, also called as ePub is a free and open e-book standard by the International Digital Publishing Forum (IDPF) and the files have the extension .epub. EPUB is designed such that the text display can be optimized for the particular display device used by the reader of the EPUB-formatted book. The format is meant to function as a single format that publishers and conversion houses can use in-house, as well as for distribution and sale.
If you plan to read ePub formats (or ebooks) on Windows, here are some of the free tools which open the .epub format.
1. AZARDI Desktop 11:
The AZARDI 11 Desktop Reader, which was released on 9 April 2012, has wide ePub2 standards support and improved support for the ePub3. One of major feature is support for SMIL audio overlays for both accessibility and general audio/text highlighting. The AZARDI Desktop Reader is targeted for the desktop and is available for Linux, Macintosh and Windows operating systems.
2. Calibre:
Calibre is free and open source e-book computer software that organizes, saves and manages e-books, supporting a variety of formats. It also supports e-book syncing with a variety of popular e-book readers and will, within DRM restrictions, convert e-books between differing formats.
3. FBReader:
FBReader is a free and open source e-book reader for GNU/Linux, Windows, and other platforms. It supports formats including EPUB, FictionBook, HTML, plucker, PalmDoc, zTxt, TCR, CHM, RTF, OEB, non-DRM’ed mobipocket (mobi), and plain-text.
4. Stanza:
Stanza is an ePub reader featuring a clean, well-organized interface that’s designed for reading all kinds of digital publications, including electronic books, newspapers, PDFs, and general web content.
5. Mobipocket Reader:
The Mobipocket software package is free and consists of various publishing and reading tools for PDA, Smartphones, cellular phones and e-book devices. It is one of the easiest way to build, organize, read and annotate your entire eBook library.
If you are using Firefox as your web browser, you can also try out EPUBReader, which is basically a Firefox add-on. With EPUBReader you can read ePub files just in Firefox, no additional software needed. EPUBReader downloads the file, makes some processing and displays the ePub file ready to read.
You may be interested to know that AZARDI desktop for Windows, Linux and Mac has been updated to AZARDI 17 and now supports IDPF Fixed layout and a lot more. The same download page link applies.