From the Summary:

Open Access book publishing in the Humanities and Social Sciences (HSS) is on the rise.
Initiatives are emerging on an international scale, ranging from providing Open Access to
single titles to full-fledged Open Access book publishers. Most of these efforts, however,
are still in the experimental phase, testing and developing new publishing and business
models as well as tracking customer behavior both online and offline. Nonetheless, some
trends and patterns are discernable.