Open access book publishing and self-archiving are developing a few years behind open access article publishing and self-archiving. The payment models in many cases are similar to OA journal articles, where authors pay for each chapter. But there are lots of experimental models.
About the future of open access books: "It seems unlikely that the core outputs of the Humanities and Social Sciences will remain closed in the longer term, while STM outputs will be required to be freely available to end users. Monographs will, at some point, become subject to a requirement for Open Access publishing –at least in most subject areas, if not all." Open Access and Scholarly Books Workshop Report – Knowledge Unlatched
There are good ways to share posters, conference proceedings, presentations, and other such work also. Zenodo, Figshare, Slideshare, Youtube, Vimeo, and other such sites are options to consider as well as WU Open Scholarship.
WU authors may use WU Open Scholarship for books and book chapters where they have the rights to distribute.
There is a growing number of institutional e-presses that produce peer-reviews open access books. This is not a comprehensive list, just a sampling of examples of sites where books and dissertations are sometimes posted.