This report seeks to understand librarians’ experiences of collective funding models for open access books, especially barriers to joining organisations like the Open Book Collective (OBC). The OBC is one of an increasing number of organisations that are using a collective 'Diamond' funding model for open access, wherein libraries commit to financially support open access book publishers, and/or open infrastructure providers for a set period of time to fund their work. The report aims to learn from differing experiences in countries with different open access policies and institutional contexts. It focuses its research on six countries in continental Europe: Finland, France, Germany, the Netherlands, Poland and Sweden. The research includes interviews with 20 participants. Most are librarians, alongside a selection of publishers and open access experts. It provides particular insight into how librarians understand collective funding models and their ability to become involved in them, within their national and institutional settings. This is supplemented by an analysis of existing research on collective funding models and a profile of each country’s current open access publishing context, based on an extensive literature review. The report will be of interest to librarians seeking to build further capacity to support collective Diamond open access funding models within their institutions, as well as publishers, infrastructure providers and collaborative endeavours seeking to build collective support for the development of open access programmes. Some key findings include: There is a strong commitment to the idea of an OA knowledge commons from librarians and researchers in many contexts across Europe. Trust in OA initiatives has been eroded by corporate buyouts, notably that of Knowledge Unlatched. Many librarians perceive a tension between committing funds to advancing the scholarly commons and meeting the needs of their institution, given ongoing pressure on budgets. Usage data from OA initiatives helps justify investment decisions, but doesn’t resolve said tensions. Dedicated budgets ringfenced for this purpose could help, but may be hard to implement in some contexts, e.g. when concrete justification is needed by funders. Transformative agreements consume most of the OA budget in some institutions. This is often the case in countries where OA policy and awareness is advanced. European librarians are concerned about the UK/US-centricity of many OA initiatives; national language publishing is seen as under-supported. Formal policies influence librarians’ OA decisions less than expected; informal decision-making, faculty opinion and networking were seen as stronger factors.