msgpack.loads will produce mutable, unhashable lists by default when unpacking values that were originally saved as dicts with tuple keys. Which ebook-convert-complete does. This results in errors when trying to reassemble the dict. Fix by allowing our msgpack wrapper to forward arguments, and by having ebook-convert-complete unpack lists as tuples.
calibre

calibre is an e-book manager. It can view, convert, edit and catalog e-books in all of the major e-book formats. It can also talk to e-book reader devices. It can go out to the internet and fetch metadata for your books. It can download newspapers and convert them into e-books for convenient reading. It is cross platform, running on Linux, Windows and macOS.
For more information, see the calibre About page
Screenshots
Usage
See the User Manual
Development
Setting up a development environment for calibre
A tarball of the source code for the current calibre release.
Bugs
Bug reports and feature requests should be made in the calibre bug tracker at launchpad. GitHub is only used for code hosting and pull requests.
Support calibre
calibre is a result of the efforts of many volunteers from all over the world. If you find it useful, please consider contributing to support its development. Donate to support calibre development.