When translating the strings in calibre, I've found several that make no sense to me. They are apparently titles, subtitles or slogans of ebook shops or sites:
"Free Books : Download & Streaming : Ebook and Texts Archive : Internet Archive." (from
http://www.archive.org/details/texts ?)
"Der eBook Shop." (from
http://www.beam-ebooks.de/ ?)
"EPUBReaders eBook Shop." (from
http://www.epubbuy.com/ ?)
"Entertain, enrich, inspire." (from
http://www.eharlequin.com/store.html ?)
There are even some strings that are definitely not English ("Zaczarowany świat książek").
What's the purpose of these? What are they used for? Should they be translated?