Among the most frequently reprinted books of the long eighteenth century, English, Scottish and American letter manuals spread norms of polite conduct and communication, which helped to connect and unify different regions of the British Atlantic world, even as they fostered and helped to create very different local and regional cultures and values. By teaching secret writing, they also enabled transatlantic correspondents to communicate what they needed despite interception, censorship and the practice of reading private letters in company. Eve Tavor Bannet uncovers what people knew then about letters that we have forgotten, and revolutionises our understanding of eighteenth-century letters, novels, periodicals, and other kinds of writing in manuscript and print which used the letter form. This lively, interdisciplinary book will change the way we read and interpret eighteenth-century letters and think about the book in the Atlantic world.