[r3bl]

Ah, too bad. It's the crappiest of the bunch UX-wise, but nothing comes close to it feature-wise.

I don't use it to read (I have an e-reader for that purpose), but I'd be lost without Calibre for ebook management.

[crooked-v]

I really wish there was a practical alternative to Calibre for general ebook organization purposes. It's extra-painful that Books.app on Mac could almost fit that role, except that it doesn't let you edit enough metadata for your own imported files to properly manage series/publisher stuff.

[qplex]

I recently used Calibre to convert a pdf to epub. I agree the UX is lacking, but it works.