The Georg Eckert Institute was founded in 1975 by the state of Lower Saxony with the mission to conduct international textbook research and to develop recommendations for education policy and publishers. However, its history began in 1951 when Georg Eckert established the International Institute for Textbook Improvement at the Kant School in Braunschweig to contribute to international understanding. From the very beginning, the textbook library served as the central foundation for this work. Today, the research library of the GEI houses the world's largest international collection of humanities and social sciences teaching and learning materials. The book presented here in its second revised edition illustrates what the GEI has accomplished in textbook revision and how it has significantly contributed to the development of textbook and educational media research. This scientific field now encompasses not only textbooks but also digital educational media and the methods of their research.