However, for a recently published (and complete) set of encyclopedias, I would think the simplest option would be to catalogue the set in one biblio. The ISBN field (020 in MARC21) is repeatable.
This is how we usually handle it, but there are drawbacks if you want people to be able to put a hold on a specific volume. Currently item-level holds can be enabled or disabled globally. If you choose to disable them, you patrons won't have a way of requesting a specific volume of your set. We have item-level holds turned off because we want the hold process to be as simple as possible, but it does cause problems when someone wants to hold a particular item. I know some folks have some developments in the works to help this situation, so I'm looking forward to seeing them. -- Owen -- Web Developer Athens County Public Libraries http://www.myacpl.org