The Chartered Institute of Library and Information Professionals has released Ebook Acquisition and Lending Briefing: Public, Academic and Research Libraries .
Here's an excerpt:
This paper presents some of the legal, strategic and technical problems that arise from the addition of scholarly and trade ebooks to library collections, together with possible solutions. Some of the most common business models are briefly set out. The latest data on ebook usage is also included.
Also of interest: ALA's recent Ebook Business Models for Public Libraries.