Librarians often wish to know whether readers in a particular discipline favor e-books or print books. Because print circulation and e-book usage statistics are not directly comparable, it can be hard to determine the relative interest of readers in the two types of books. This study demonstrates a two-step method by which librarians can assess the appeal of books in various formats. First, a nominal assessment of use or nonuse is performed; this eliminates the difficulty of comparing print circulation to e-book usage statistics. Then, the comparison of actual use to Percentage of Expected Use (PEU) is made. By examining the distance between PEU of e-books to PEU of print books in a discipline, librarians can determine whether patrons have a strong preference for one format over another.