Sigil is a multi-platform WYSIWYG ebook editor. It is designed to edit books in ePub format.

Now what does it have to offer...

• Free and open source software under GPLv3
• Multi-platform: runs on Windows, Linux and Mac
• Full Unicode support: everything you see in Sigil is in UTF-16
• Full EPUB spec support
• WYSIWYG editing
• Multiple Views: Book View, Code View and Split View
• Metadata editor with full support for all possible metadata entries (more than 200) with full descriptions for each
• Table Of Contents editor
• Multi-level TOC support
• Book View fully supports the display of any XHTML document possible under the OPS spec
• SVG support
• Basic XPGT support
• Advanced automatic conversion of all imported documents to Unicode
• Currently imports TXT, HTML and EPUB files; more will be added with time
• Embedded HTML Tidy; all imported documents are thoroughly cleaned; changing views cleans the document so no matter how much you screw up your code, it will fix it (usually)
• An actually usable user interface
• Native C++ application
• Bugs :)
• And a lot more...

Don't forget to read the online manual!.

If you wish to discuss Sigil, feel free to do so on the Sigil subforum on MobileRead. Also check out the wiki pages, especially the installation instructions. For those who want more up-to-date information on Sigil's development, you can always take a look at the live ChangeLog. That file is linked directly from the repository, and it is updated as bugs are fixed and features are added. You can also subscribe to RSS and Atom feeds.

If you found a bug or want to request a feature, read the ReportingIssues wiki page.

Also feel free to check out Sigil's development blog. Information on how to donate can be found on the Donate wiki page.