For researchers of education, textbooks can be a vital primary source. They provide information about the evolution of school curricula over time, about changing ideas, practices, and methods in teaching and assessment. History and geography textbooks especially contain representations of everyday life and dominant attitudes of the past and in different regions of the earth. These representations are the reflection of a changing historical ideological and social context. As these textbooks are often commissioned or approved by state authorities, they can also be powerful tools of social engineering and may provide cues to the process of nation-building. They give a projection of official visions of how a society should look like, its degree of equality, and its treatment of those who othered and excluded. Consequently, textbooks can provide information about class and socio-economic inequality, just as about the treatment of women, migrants, or the disabled. Textbooks may not only be a means to justify practices that create inequality, for example in the context of dictatorship or colonialism, but also as an instrument for liberation from such practices, in the context of decolonization. In times of conflict, textbooks may exacerbate tension through a certain depiction of “the enemy”. On the other hand, they have the potential to improve social cohesion and international understanding. The newly digitized IBE Textbook Collection may thus help researchers to answer a great number of different historical questions and to inform contemporary problems in textbook research.