This book systematically investigates the depositional process and reservoir characteristics of organic-rich shales, including (1) The types and development mechanisms of organic-rich shales under ancient ocean and climatic backgrounds. Schematic models are proposed to understand the organic matter enrichment and depletion in shale systems. (2) Microstructure and petrophysical properties. The general lithofacies are recognized and linked to the depositional setting and petrophysical properties. Full-scale pores and fractures are characterized using FE-SEM, gas adsorption, nano-CT and micro-CT scanning. (3) Brittle-ductile characteristics. Rock mechanical properties and in-situ stress are determined. The brittle-ductile transformation of shales is discussed. (4) Shale gas occurrence state and differential enrichment. Gas content and dynamic dissipation over geological time are evaluated using sorption experiments and numerical simulation. Shale gas enrichment model is developed to understand the gas differential accumulation in organic-rich shales. This book can be used for reference by researchers engaged in shale oil and gas geology in both academics and industry.