In early 2022 UKRI released a policy statement mandating OA monographs, with an implementation date of January 1st, 2024. This date will see a shift from a hypothetical future for OA books to a concrete policy with a hard deadline. In Europe, cOAlition S/Plan S have mooted an OA books policy and here in the UK there are also potential implications of the next REF. So it seems clear there is a pressing need for libraries and academic book publishers to grapple with the challenges and opportunities now. And perhaps chief among those is the question of how this 'new normal' of OA books will be paid for. The transition to OA should not leave smaller and medium-sized presses behind; nor should it rely on paying BPCs, which risks excluding any author without funding. And the transition must be sustainable for libraries. We'll demonstrate how BPCs worsen inequality by favouring the most wealthy institutions and authors, and we'll highlight some collective library funding efforts that seek to spread the funding of OA books so that no single institution bears a disproportionate cost. With the clock ticking on imminent policies, conversation is urgently needed on the practicalities of making mandates reality. We'll discuss what libraries can do to meet the challenge, and how supporting collective programmes will ensure that the transition to OA is a sustainable and bibliodiverse one. This session will feature two-way dialogue, perhaps even using breakouts if there are enough attendees. COPIM's role will be to recap the issues, keep ideas flowing, capture interesting points, prompt and even provoke the audience with challenging questions. We want to hear from expert library colleagues discussing practical ways in which libraries can get involved. We want to ask them as the experts how they are supporting, funding, advocating for, and sustaining OA monographs at their institution.