I had an idea for a plugin that facilitates tagging your books with
BISAC codes .
Basically, it would create a custom column called "BISAC" and will allow you with an easy to use GUI (I wonder if one can programmatically add another tab to the Edit Metadata dialog?) to add BISAC codes, separated by commas.
Then, you can use the plugin to populate another column using the BISAC hierarchy. For example, if you have a custom Genre(s) column, then for every book, the plugin would translate the BISAC codes into hierarchical strings (e.g. History.General, Fiction.Myster.etc...).
Using these standardized genres will make it easy for people like me who aren't aware of good category names and want a standardized way of cataloguing their books.
Is there anyone that might be interested in something like this?