I can make myself feel all important by saying I have a Release Candidate for Bookcase. Actually, I just wanted to give the couple of folks who offered to do translations a chance to update them before I put together the Bookcase 0.5 tarball. I fixed a pretty big bug with latin2 character sets, added some GUI enhancements, and a new printing configuration dialog. My XSLT files are horrible crap and needlessly messy, but they seem to get the job done.
The format of the Bookcase data file has changed. So version 0.5 can read 0.4 just fine, but don't try to open a file you saved from version 0.5 in version 0.4 because you'll lose some data. I'm updating the DTD, of course. Basically, the entries where I had them separated by a semi-colon in the data file, I broke apart into separate elements. Makes for easier parsing from XSLT, in particular.
I didn't get around to adding an internet query or lookup function. I'm working on a KIO slave for the z39.50 protocol, which should allow for online searches via ISBN or what-have-you, but it's rather tricky. I think that'll be in the next version.
Update: Bookcase 0.5 is released, so I removed the release candidate.