George Washington's Rules of Civility and Decent Behaviour in Company and in Conversation by George Washington (naturally)
Our local library has a summer reading program for adults as well as for children. One of the things to accomplish is to read something from their Choose Civility reading list. Looking at the list, this book by George Washington jumped out at me and I knew I had to read it.
The book consists of 110 rules "drawn from an English translation of a French book of maxims" [p. 7] by Washington. The syntax is a bit archaic (rule 2: "When in company, put not your hands to any part of the body, not usually discovered") but that naturally forces modern readers to pay attention to the detail and meaning of what is written. Also, the phrasing is charming (rule 12: "Shake not the head, feet, or legs; roll not the eyes; lift not one eyebrow higher than the other; wry not the mouth; and bedew no man's face with your spittle by approaching too near him when you speak").
The rules cover all sorts of behavior from walking to conversing to dining. They are eminently civilized and practical (rule 48: "Wherein you reprove another be unblameable yourself, for example is more prevalent than precepts") and hardly seem in practice in modern culture (rule 58: "Let your conversation be without malice or envy, for it is a sign of a tractable and commendable nature; and in all cases of passion admit reason to govern"). I'm sure that people in the 1700s had just as many challenges as moderns have when it comes to dealing with other people in a civil manner.
The edition I read was 30 pages long, so it reads very quickly. It also provides very valuable insight into what people thought was important 250 years ago and what we can improve upon today.