I asked about the book sharing concept at the newgenlib mailing list. Here is their response: We would like to first appreciate this innovative concept of lending > library. > As you have mentioned for this concept we either need to implement an ILL > or Network library to realize this. > ILL is available in NGL in Circulation functionality. > However from a "traditional" library's point of view an item loaned on ILL > basis is usually meant for one patron only. Once the patron is done with the > item it is returned back to the lending library. Which is not your case! > Using Library network will be heavy weight. > Also, most of the books in a library are its own property, hence accession > numbers are provided for them. > > As of now NewGenLib does not meet the such requirements. We will consider > this business case in our next development cycle. > I expect any other ILS not designed for book sharing would have the same limitations in their ILL system.