There are a variety of ways to request items that the University Libraries do not currently own, or that are currently unavailable because all copies are being used. Visit this page to see them (http://guides.library.unlv.edu/interlibraryloan/) . Often you will receive a pdf copy sent to your UNLV email account, or the physical item will be sent to the library and made available to you for a few weeks. This service is free to UNLV faculty, staff, and students!
More Ways to Discover Books
You can use Hathi Trust, WorldCat, and Google Books to search for books all over the world.
Search this database listing books in libraries worldwide to discover what's been published on a subject. The Get Text button will link you to a Document Delivery Services form to request books from other libraries.