Objective – To present the initial results of an academic library’s one-year pilot with patron-driven acquisition of e-books, which was undertaken “to observe how user preferences and the availability of e-books interacted with [the library’s] traditional selection program” (p. 469). 
 
 Design – Case study.
 
 Setting – The University of Iowa, a major urban research university in the United States.
 
 Subjects – Original selection of 19,000 e-book titles from ebrary at the beginning of the pilot in October 2009. To curb spending during the pilot, the number of e-book titles available for purchase was reduced to 12,000 titles at the end of December 2009, and increased to nearly 13,000 titles in April 2010. 
 
 Methods – These e-book titles were loaded into the library’s catalogue. The goal was for the University of Iowa’s faculty, staff, and students to search the library catalogue, discover these e-book titles, and purchase these books unknowingly by accessing them. The tenth click by a user on any of the pages of an e-book caused the title to be automatically purchased for the library (i.e., ebrary charged the library for the e-book). 
 
 Main Results – From October 2009 to September 2010, the library acquired 850 e-books for almost $90,000 through patron-driven acquisition. The average amount spent per week was $1,848 and the average cost per book was $106. Researchers found that 80% of the e-books purchased by library patrons were used between 2 to 10 times in a 1-year period. E-books were purchased in all subject areas, but titles in medicine (133 titles purchased, 16%), sociology (72 titles purchased, 8%), economics (58 titles purchased, 7%), and education (54 titles purchased, 6%) were the most popular. Two of the top three most heavily used titles were standardized test preparation workbooks. In addition, 166 of the e-books purchased had print duplicates in the library, and the total number of times the print copies circulated dropped 70% after the e-versions of these books were obtained.
 
 The authors also examined usage data for their subscription to ebrary’s Academic Complete collection from September 2009 to July 2010, which consisted of 47,367 e-books. Together with the 12,947 book titles loaded into the catalogue for the patron-acquisition pilot, there were a grand total of 60,314 ebrary e-book titles in the library catalogue that were accessible to the Iowa University community. The study revealed that 15% of these titles were used during this 11-month period, and the used titles were consulted 3 or more times. The authors sorted the user sessions by publisher and found that patrons used e-books from a wide variety of publishing houses, of which numerous university presses together constituted the majority of uses. The five most heavily used e-books were in the fields of medicine, followed by economics, sociology, English-American literature, and education. 
 
 Conclusion – The authors’ experience has shown that patron-driven acquisition “can be a useful and effective tool for meeting user needs and building the local collection” (p. 490). Incomplete coverage of academic publications makes patron-driven acquisition only one tool among others, such as selection by liaison librarians, which may be employed for collection development. According to the authors, patron-driven acquisition “does a good job of satisfying the sometimes 
 unrecognized demand for interdisciplinary materials often overlooked through traditional selection methods,” (p. 491) and alerts librarians to new research areas.