That You’d Tell All Your Friends

Followup to: The Most Frequently Useful Thing

What’s the number one thing that goes into a book on rationality, which would make you buy a copy of that book for a friend? We can, of course, talk about all the ways that the rationality of the Distant World At Large needs to be improved. But in this case—I think the more useful data might be the Near question, “With respect to the people I actually know, what do I want to see in that book, so that I can give the book to them to explain it?”

(And again, please think of your own answer-component before reading others’ comments.)