The Origin of the Shape of Books

Codex was used originally to distinguish a book, as we know it today, from its ancestor, the scroll. By Patrick’s time the codex had almost universally displaced the scroll, because a codex was so much easier to dip into and peruse than a cumbersome scroll, which had the distinct disadvantage of snapping back into a roll the moment one became too absorbed absorbed in the text. The pages of most books were of mottled parchment, that is, dried sheepskin, which was universally available – and nowhere more abundant than in Ireland, whose bright green fields still host each April and explosion of new white lambs. Vellum, or calfskin, which was more uniformly white when dried, was used more sparingly for the most honored texts… It is interesting to consider that the shape of the modern book, taller than wide, was determined by the dimensions of a sheepskin, which could most economically be cut into double pages that yield our modern book shape when folded.

Cahill, How the Irish Saved Civilization, p. 168

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