Calibre has a "good UI" the way GIMP and QGIS have "good UI"s. They're opinionated, idiosyncratic power tools in spaces where a large part of the audience don't

Calibre has a "good UI" the way GIMP and QGIS have "good UI"s. They're opinionated, idiosyncratic power tools in spaces where a large part of the audience don't want to learn a UI that doesn't resemble those of more popular or initiative tools in the same space. It took me the better part of the year to figure out how and why QGIS wouldn't just let me draw geometry like I can in a vector drawing tool. I still have to read the docs every time to figure out most selection manipulation actions in GIMP or decode the icons. With Calibre and GIMP in particular, most people don't need most of its functionality, and easier but weaker tools exist that can do the same things. Almost all of my image editing is in Krita now because it's about as powerful and much more intuitive. If Citadel becomes the Krita of ebook readers, I'd readily use it just on the UI even if it's just as unstable.