This AAPG Memoir on the Haynesville Shale of East Texas, USA, provides an overview of the main geologic, stratigraphic, sedimentologic, geomechanical, micro-seismic and engineering characteristics of the Haynesville mudrocks. Experts on mudrocks from academia, industry, and government contribute with a variety of topics that describe the Haynesville Shale from basin- to nanaoscale, reflecting the dimensions affecting shale-gas assessment and demonstrating the variety of techniques applicable to shale-gas evaluation. The included papers serve not only as examples of shale-gas analyses of the East Texas shale basin employing different techniques, but also are examples of approaches to evaluating shale basins worldwide.