The interest in the use of electronic media in scholarly communication is growing. Nowadays, libraries reserve much larger budgets for electronic information sources as users tend to get access to the full-texts of journal articles and books online. The effective management of library collections is only possible through studies identifying user needs as well as studies of usage analysis showing how much of what is being used in these collections. Although e-books are a significant part of library collections, studies on e-book use are scarce. In this paper, we have analyzed about half a million use data of ebrary e-book database by the users of Hacettepe University Libraries within a four-year period (2006-2009). We obtained COUNTER-compliant use data identifying, among other things, book title, publisher, and publication year for each transaction to analyze the use. We identified the most frequently used e-book titles by Hacettepe University ebrary users in each Library of Congress (LC) subject class. E-books on Medicine (R) were used most often, followed by books on Education (L) and Language and literature (P). A small number of e-books in each subject class satisfied half the demand, while an overwhelming majority of e-book titles were never used. Findings of this study can be used to develop an e-book collection management policy and understand its implications for consortial licensing of e-book packages.