Often UWG Library does not have a book, but can borrow it from another USG Library through the service GIL Express. GIL Express is a service you have already paid for with your tuition and using it does not cost you any extra money. This is usually the case if you search for a book in the USG catalog and the book's record says "Check holdings."
If no USG Libraries have the book, in most cases you can request it through Resource Sharing (also known as Interlibrary Loan or ILL). Please note that Resource Sharing cannot provide some items, including e-books, reference books, and special collections items.