Sigil

Sigil is a multi-platform WYSIWYG ebook editor. It is designed to edit books in ePub format.
Features:
- 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
- Currently exports EPUB and SGF (Sigil native format); 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