When I've listed Antiquarian books, like those I have currently listed, I've been able to create custom categories.
Here's a good example of one of my auctions with a little creativity (see the Sub-Category):
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item...=STRK:MESO:IT&ih=010
All the Item specifics were created in the Auctiva listing.
Dan