Sigil is a multi-platform EPUB ebook editor with the following features

• Online Sigil User's Guide, FAQ, and Wiki documentation
• Free and open source software under GPLv3
• Multi-platform: runs on Windows, Linux and Mac
• Full UTF-8 support
• Full EPUB 2 spec support
• Multiple Views: Book View, Code View and Split View
• WYSIWYG editing in Book View, supporting all XHTML documents under the OPS specification
• Complete control over directly editing EPUB syntax in Code View
• Table of Contents generator with multi-level heading support
• Metadata editor with full support for all possible metadata entries (more than 200) with full descriptions for each
• User interface translated into 15 languages
• Spell checking with default and user configurable dictionaries
• Full Regular Expression (PCRE) support for Find & Replace
• SVG support and basic XPGT support
• Supports import of EPUB and HTML files, images, style sheets, and fonts
• Documents can be validated for EPUB compliance with the integrated FlightCrew EPUB validator
• Embedded HTML Tidy: all imported files have their formatting corrected, and your editing can be optionally cleaned
• Native C++ application

If you wish to discuss Sigil, feel free to do so on the Sigil Forum at MobileRead. Don't forget to read the online Sigil User's Guide, and also visit the Wiki pages, especially the FAQ and the Installation Instructions. For a list of all changes made to Sigil, you can view the Sigil Changelog or even track updates as they happen.

If you found a bug or want to request a feature, please read the Reporting Issues 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.