Bookcase 0.4 is released. I fixed a few bugs, added a toolbar with a combobox for selecting which property to group the books by, and improveed the printing layout a bit.
I've learned more about XSLT than I ever wanted to know. You can't use a parameter in the key() function, which limited me since I wanted to pass in the parameter from Bookcase. So I went a different route, much more inefficient, of doing two different sorts in the XSLT file. I also took advantage of the EXSLT extensions in libxslt which means at least version 1.0.19 is now required.