Publishers might be able to determine when interest in a fiction series is flagging if readers who bought and finished the first twobooks quickly suddenly slow down or quit reading laterbooks in the series.
All that Palladio learned from Vitruvius and from twolater trips to Rome in the 1540s became the basis of the most influential books on architecture ever written, his Quattro Libri dell'Architettura, published in Venice in 1570.