Part of the problem, though, is simply that there's no really good common "interchange format" for ebooks. All of the currently available formats (ePub, MOBI, HTML, PDF, FB2...) are effectively meant for direct consumption by some sort of device or another, so converting them to other formats is a messy process. I'm currently working on a simple new format for authoring (fiction) books in, as well as tools for converting this to all the other formats that matter; anyone interested in helping? :)
The format I'm planning to use as the intermediate is basically just a restricted subset of HTML. I'm primarily targeting fiction texts with this format, so advanced formatting isn't generally necessary.
calibre calls that; so can you.
The lack of command-line tools that avoid pulling in hundreds of QT dependencies that I do not need (not to mention Calibre itself) is rather annoying.
Anyone who forks Calibre and gives it a useful GUI; or creates what people actually need (X-to-Y format shifting tools) without all the weird cruft that Calibre has (original article fails to mention that "add books" creates a bunch of folders in odd places) would be very popular.