Calibre 5.0 - https://news.ycombinator.com/item?id=24586455 - Sept 2020 (267 comments)
Calibre 4.0 - https://news.ycombinator.com/item?id=21156482 - Oct 2019 (302 comments)
The Calibre Content Server - https://news.ycombinator.com/item?id=14568146 - June 2017 (140 comments)
Announcing Calibre 2.0 - https://news.ycombinator.com/item?id=8212885 - Aug 2014 (98 comments)
Calibre version 1.0 released - https://news.ycombinator.com/item?id=6271090 - Aug 2013 (121 comments)
Calibre and Project Gutenberg: Liberate Your eReader. - https://news.ycombinator.com/item?id=3750807 - March 2012 (18 comments)