Time was when readers kept commonplace books. Whenever they came across a pithy passage, they copied it into a notebook under an appropriate heading, adding observations made in the course of daily life. Erasmus instructed them how to do it; and if they did not have access to his popular De Copia, they consulted printed models or the local schoolmaster. The practice spread everywhere in early modern England, among ordinary readers as well as famous writers like Francis Bacon, Ben Jonson, John Milton, and John Locke. It involved a special way of taking in the printed word. Unlike modern readers, who follow the flow of a narrative from beginning to end, early modern Englishmen read in fits and starts and jumped from book to book. They broke texts into fragments and assembled them into new patterns by transcribing them in different sections of their notebooks. Then they reread the copies and rearranged the patterns while adding more excerpts. Reading and writing were therefore inseparable activities. They belonged to a continuous effort to make sense of things, for the world was full of signs: you could read your way through it; and by keeping an account of your readings, you made a book of your own, one stamped with your personality.
See Darnton’s original article.