A group of major universities has been quietly working for the past two years to build one of the largest online collections of books ever assembled, by pooling the millions of volumes that Google has scanned in its partnership with university libraries. One of the most important functions of the project, say its leaders, who unveiled the giant library in October 2008, is to create a stable backup of the digital books should Google go bankrupt or lose interest in the book-searching business. The project is called HathiTrust, and so far it consists of the members of the Committee on Institutional Cooperation, a consortium of the 11 universities in the Big Ten Conference and the University of Chicago, and the 10 campuses in the University of California system. The University of Virginia just joined the project, and officials hope to bring in other colleges as well.