* Make calibre timezone aware. This required lots of internal changes, so I may have broken something
* Allow editing of metadata in DRMed MOBI files
* ebook-convert: Allow passing URLs as argument to –cover
* OS X/linux driver for EB511
* ebook-meta: Allow changing of published date
* Make replacing of files in ZIP archives faster and (hopefully) more robust
* Speed optimization for viewing large EPUB files
* Speed up parsing of OPF files
Plus numerous bug fixes.
0.6.42 was release shortly afterwards with a couple of bug fixes.
http://calibre-ebook.com/