Use the Discovery box to search for books that Shippensburg may own. It will bring up a variety of resources, all that belong to Shippensburg. Once you're redirected to the results list, you may narrow it down to Books by checking them off under Source types; you may also uncheck "Available in Library Collection" to search for books outside of the university that you can send for via Interlibrary Loan. (To learn how to set up your ILLIAD--interlibrary loan--acccount, view this video: Setting Up and Using ILLIAD).
Use the library catalog below to search for only books in Lehman Library. Use WorldCat below to search for books only around the country and even world (again, limit results to "Books" in source types).
In the bottom section are links to encyclopedic databases; keep in mind that this information is typically used for background only and would not be considered part of your scholarly sources.