There are many resources to use to find books at UCSD, as well as the broader San Diego, California, and Global Community. Begin by searching ROGER to find books available at UCSD. If there are no hits, you can broaden your search by using MELVYL to search for books available throughout the University of California System. CIRCUIT can be used to do a San Diego-specific libraries such as SDSU and San Diego Public Library.
You can also search WorldCat. This is a world-wide, consortial catalog of OCLC member libraries that includes over 50 million online records in multiple formats. This is the best place to look for a particular source that is not held in California, or to do a search by subject heading(s) to find materials outside of California.