The work of all medievalists is fundamentally dependent on medieval books. Written information transmitted through books supplies historical context and often constitutes a primary object of study. Scholars have long based their research on the written, printed, pictorial and decorative contents of individual books and classes of book from the middle ages. It is hardly surprising that less attention has been paid to books as cultural artefacts, i.e. objects that are recognised and understood in particular ways and defined according to given criteria. While most people recognise the symbolic value of books, few devote much attention to it, and the assumptions on which the definition of the medieval book rest have provoked little interest to date. Yet the subject raises important questions.