Previous research has indicated a decreased use of textbooks among religious education teachers, while students with a religious background perceive themselves as a vulnerable minority in classrooms. It also points to a post-Christian society where schools now take responsibility for knowledge about the Christian faith and how it should be understood. Simultaneously, secularization is increasing in society, and people express a secularist attitude towards religion. The aim of this essay is to examine the representation of Christianity in religious education textbooks for upper secondary school based on secular and secularist discourses, and analyze how the results can be interpreted in terms of the concepts of alliance, othering, positive essentialism, and negative essentialism. The theories that were utilized included modified secularization theory, discourse theory, and essentialism in religious education. These were combined with the methods of discourse analysis and critical discourse analysis. The conclusion from this study is that in the selected books, positive and negative essentialism occurred to varying degrees, indicating a lack of objectivity. There were also numerous alliances and instances of othering, which in several cases suggested secular and secularist discourses.