SlackBuildsOrg/office/calibre

Calibre is meant to be a complete e-library solution. It includes library
management, format conversion, news feeds to ebook conversion as well
as e-book reader sync features.

Calibre is primarily an ebook cataloging program. It manages your ebook
collection for you. It is designed around the concept of the logical book,
i.e. a single entry in the database that may correspond to ebooks in
several formats. It also supports conversion from a dozen different ebook
formats to LRF and EPUB. A graphical interface to the conversion software
can be accessed easily by just clicking the "Convert E-books" button.