OAPEN-UK has released OAPEN-UK Final Report: A Five-Year Study into Open Access Monograph Publishing in the Humanities and Social Sciences .
Here's an excerpt from the announcement:
Examining the attitudes and perceptions of funders, researchers, publishers, learned societies, universities and libraries, our study reiterated the deep strength of feeling and connectedness that each group has with the monograph, especially in terms of identity and reputation. It also found that while many think open access is a good idea in principle, there is uncertainty about how easy it would be to implement the necessary policies and systems to support OA monographs.