This document discusses initiatives to support open access publishing of books in the humanities and social sciences. It outlines the OPERAS initiative, which aims to: [1] adopt common standards for European open access book publishing; [2] share research and development projects; and [3] advocate for open access in the humanities. OPERAS currently has 12 partners from 5 countries and seeks to establish a sustainable infrastructure for open access publishing of books at a European scale. The long term goal is for OPERAS to be recognized as a research infrastructure by the European Strategy Forum on Research Infrastructures.