Sigil is an open source ebook editor that runs on GPLv3. Sigil Writing follows the principles of WYSIWYG (what you see gets) and works much like any other text editing program, such as Microsoft Office.

Sigil can now import files in TXT, HTML and EPUB formats. Import in EPUB and SGF (Sigil native format).

This program is very easy to use and very early in development, but it offers interesting possibilities for those who own ebooks.