I posted a brief announcement in another thread, but in case you didn't notice that, a new Spotlight plugin for ePub files has been released together with an updated Quicklook plugin.
I'd be interested in any feedback here (I helped write the Spotlight importer, and hacked on the core code a bit) but if you want to raise an "Issue" yourself on github please do so.
: the download DMG had some bad links, please try again!
It indexes quite a few bits of ePub 2 metadata, as well as the textual content of unprotected books. Indexed metadata includes:
In addition it tries to detect the variant of DRM being used (Apple, Adobe, Kobo, Barnes & Noble) and for expiring (e.g. library) books, their expiry date.