The textbook is a document of great importance from primary through secondary education, and it would not be an exaggeration to regard it as the written constitution of any country. It has been defined as "a printed and structured instrument intended to engage learners in a learning pathway with a view to improving its effectiveness and quality", and as "the principal and primary tool of the educational process, since it contains the teaching material in an organized manner that helps the pupil to remember that material or to return to it". The teacher should not treat the textbook as the sole reference of the educational process or as the only source of the knowledge the pupil acquires; rather, it is an organized tool that assists the pupil in this endeavour. The textbook is a cornerstone of the educational and teaching process, and without it pupils' knowledge would be lost. Textbooks vary according to level, subject and syllabus. It follows that the textbook is indispensable, and that writing about it, and within it, requires the researcher to bring to bear the full weight of pedagogical, scientific, psychological and social knowledge in order to convey its importance and the issues surrounding it. In this paper we have sought to address several points, moving between the general and the specific and summarizing where appropriate.