The Call Number for a book starts with "XX." What does that mean?

Answer: 

An XX call number can mean one of two things. First, it can mean that we have ordered an item for the library, but it is not on the shelf yet. If that is the case, the catalog record will say "in process" or "on order." Secondly, it can mean that an item is actually an electronic document. In that case, there will be a link to the document in the catalog record.