Format: The format is the technical and bibliographical term for the shape of the book, defined by the number of times each printed sheet is folded. Determined during the "casting off" or planning period, format determined the amount of paper used, affecting both the cost and size of the final book. Common formats include:
folio - one fold
quarto - two folds
octavo - three folds
The folio was often used for expensive, presentation volumes and important religious books. Quartos were used for popular books, such as novels, tracts, and plays. Octavo books fit nicely in the hand, and were prized for their portability and reduced production costs.