This document summarizes the key requirements for open access publication of books and monographs under Horizon Europe, the EU's research and innovation program. It outlines that immediate open access without embargo is required for books/monographs through both publishing and repository open access. CC BY or CC BY NC/ND licenses are mandatory. Publication fees will only be eligible if full open access is provided. The document also discusses potential approaches to financing open access books, including book processing charges, transformative arrangements to support publisher transitions, and sustained support for nonprofit publishing models.