The IIP-Ecosphere platform is a central asset developed by the IIP-Ecosphere project. The core aim of the platform is to research and demonstrate novel platform concepts for Industry 4.0, e.g., asset administration shells as interfaces for software components and resources, unified edge deployment, an AI toolkit or seamless configuration of a platform from network settings via services up to applications running on the platform. This platform handbook provides insights into the rationales, ideas and concepts that make up the design and the realization of the IIP-Ecosphere platform, ranging from an overall layered architecture over a detailed discussion of the design and realization state of each layer up to cross-cutting mechanisms such as the configuration model or the related code/artifact generation. This platform handbook addresses the technical side of the platform work in IIP-Ecosphere and builds on the intensive prior work on requirements (usage view and functional/quality requirements of the platform). This handbook shall provide means for deeper technical discussions with partners, stakeholders and interested parties, but also allow for a technical understanding to contribute to the platform, e.g., in terms of protocols, platform connectors, services or demonstration applications. This version of the handbook focuses on the platform release as of March 2023 (version 0.5.0) and supersedes older versions of this handbook/the platform. This artifact contains version 0.5.0 in accordance to the release version on Github. We will update this document with the next release of the IIP-Ecosphere platform.