Angela Conyers et al. have published "E-book Usage: Counting the Challenges and Opportunities" in Insights: the UKSG Journal.
Here's an excerpt:
This article summarizes how libraries and library consortia are acquiring and evaluating e-books, how usage statistics feature within library workflows, the issues faced in doing so and the resulting impact of these issues on understanding usage and informing purchasing of new titles. Discussions with publishers indicate how usage data are being used within the organization, the requirements of customers and the challenges involved in providing usage data for e-books. Assessing and evaluating e-book usage is a complex and challenging task with processes and workflows in development. A transition from print to e-books represents a significant change for libraries, and the availability of reliable usage statistics to support purchase decisions is vital.
Digital Curation and Digital Preservation Works | Open Access Works | Digital Scholarship | Digital Scholarship Sitemap