Interest in publishing Open Access books has been growing in recent years, and many publishers now offer open access publication options for books.
Several programs and initiatives are supporting Open Access book publishing in various ways, such as the TOME Initiative or the UC Press Luminos Program (UC Davis Library is supporting both).
To find a publisher for an Open Access book you can consult the OAPEN OA Books Toolkit.
UC's Office of Scholarly Communication has more information about Open Access book publishing on their website.