I started using Calibre sometime in the 2011-2012 timeframe. At first, the whole interface and the logic behind it threw me completely, and I nearly gave up on it. On the day I was going to try for the last time to understand Calibre, it all came together for me, and it just clicked. Lucky me

. Since then, I have used it regularly, with a huge learning curve over the years with epub, hmtl, formatting, and of course those pesky regexes. But very happy I have spent the time learning it all. And still learning....
Thanks for a brilliant piece of software, that is a permanent companion to my love of books.