Version 4.0 of the
Calibre ebook management application is out. “It has been two years since calibre 3.0. This time has been spent mostly in making the calibre Content server ever more capable as well as migrating calibre itself from Qt WebKit to Qt WebEngine, because the former is no longer maintained.

The Content server has gained the ability to Edit metadata, Add/remove
books and even Convert books to and from all the formats calibre itself
supports. It is now a full fledged interface to your calibre
libraries.“

Source: LWN.net – Calibre 4.0 released