the latest issue of Jisc Inform includes "Innovative Approaches to Publishing Open Access Monographs It's Not Business as Usual."
Here's an excerpt:
If open access policies start to include monographs (the Wellcome Trust in May 2013 expanded its open access policy to include funding for authors of monographs and book chapters), what business model will support a vibrant HSS research environment and the wide dissemination of knowledge, and at the same time be affordable and sustainable for all the parties involved, especially those without grant funding?
There is little evidence on different open access models and so there is currently a period of experimentation. Let's look at the business models currently being explored.