Great to hear. If anyone needs an assist on how to integrate the AppImage into your Desktop (like I believe PeterT has done), just let me know.
For me, it's merely a matter of putting a Sigil.desktop file in ~./local/share/apps (with the Exec line pointing to wherever the appimage is), and adding a ~./local icon that the desktop file can pickup. After that, the Sigil AppImage can be launched from menus, and it can be set as the default handler for epubs. I'll try to post a sample .desktop file when I get a minute.
EDIT:
Here's the contents of my desktop file
Code:
[Desktop Entry]
Type=Application
Name=Sigil
Comment=ePUB file editor
TryExec=~/appimages/Sigil-x86_64.AppImage
Exec=~/appimages/Sigil-x86_64.AppImage %F
Icon=sigil
Categories=Office;
MimeType=application/epub+zip;
That requires that a "sigil" icon be available in one of the usual icon places.