.kfx is new format is released with the Kindle paperwhite 3, if user download kindle ebook by USB cable, you find this .kfx format file, our converter doesn’t support .kfx format, you get follow error message.
raise DrmException(u"Invalid file format")
DrmException: Invalid file format
We can remove drm from kindle .kfx ebook, the key thing is download ebook in amazon app “Kindle for PC” in windows, or “Kindle for Mac“ in Mac, this is tutorial how to remove drm from .kfx file.
2 Run Kindle for Pc, or Kindle for Mac, goto “Library->All items” in Kindle app,
find ebook title right click, select “Download” item to download ebook.
4 Click “Kindle” button to import ebook file download by Kindle Pc,
you can import “new ebook” only, there is setting at bottom,
5 Click “Converter” button to remove ebook drm file, you get new nodrm file in output folder when it done.