The book deals with a new scientific approach developed under the Title of General Subject Didactics. This concept is based on the existence of several academic disciplines called Subject(-matter) didactics or disciplinary didactics (as in many parts of Europe) or Subject pedagogies (as in Japan, for example), which have content-based teaching and learning in school and beyond as their object of study. General Subject Didactics can be defined as the theory of Subject didactics. It observes and reflects on how the individual Subject didactics explore Subject-specific teaching and learning, both by top-down reflections and by bottom-up comparisons. The empirical basis derives from a comprehensive study in Germany where 17 Subject didactics were compared on the basis of six impulses, e. g. reference sciences of Subject didactics, sources and selection of Subject content or research formats applied. This allows to gain insights into the commonalities of all related disciplines and to identify differences among them. Both are commented upon by four international experts, three from Europe and one from Israel.