HIRMEOS will improve five important publishing platforms for the open access monographs in the SSH and enhance their technical capacities and services, rendering technologies and content interoperable and embedding them fully into the European Open Science Cloud. The project focuses on the monograph as a significant mode of scholarly communication in the SSH and tackles the main obstacles of the full integration of important platforms supporting open access monographs and their contents. HIRMEOS will prototype innovative services for monographs in view of full integration in the European Open Science Cloud by providing additional data, links and interactions to the documents, paving the way to new potential tools for research assessment, which is still a major challenge in the SSH. The platforms participating (OpenEdition Books, OAPEN Library, EKT Open Book Press, Ubiquity Press and Göttingen University Press ) will be enriched with tools that enable identification, authentication and interoperability (DOI, ORCID, Fundref), and tools that enrich information and entity extraction (INRIA (N)ERD), the ability to annotate monographs (Hypothes.is), and gather usage and alternative metric data. HIRMEOS will also enrich the technical capacities of the Directory of Open Access Books (DOAB), a most significant indexing service for open access monographs globally, to receive automated information for ingestion, while it will also develop a structured certification system to document monograph peer-review. Partners will develop shared minimum standards for their monograph publications, such that allow the full embedding of technologies and content in the European Science Cloud. Finally, the project will have a catalyst effect in including more disciplines into the Open Science paradigm, widening its boundaries towards the SSH.