Hi there! New user here. I filed an enhancement report and Kovid suggested I redirect my request over here.
Have any of y'all ever seen or used ISFDB.org, the Internet Speculative Fiction Database? It is an incredibly thorough and useful database, accurate to the best of my knowledge and well-researched, containing publication information and cover art (as available) for every edition of a title in the speculative fiction, science fiction and fantasy fields. I use it almost daily. It is a wonderful resource.
It seemed to me that it should be a shoo-in as a metadata download source for Calibre, and I didn't see it included in the metadata download sources nor a way to add one manually. Kovid replied:
"Metadata sources can be added to calibre as plugins. There are a large
number of such plugins available (I cant recall offhand if there is one
for ifsdb) which you can install from Preferences->Plugins. If there is
no plugin for ifsdb you can either create one yourself or request that
someone create it for you in the calibre forums at mobileread.com"
And here I am.

I'd have no idea how to implement such a thing, though. Would anyone have any interest?
Thanks!
Chuck