The first book in this series to be written by a different author.
I don't like the organization as well as in the first three books, but it does contain a lot of interesting info.
How the measure of floor size was, prior to this time, in floor mats, and here is where chairs came in. The increasing number of concubines, even when the primary wife was not barren. The changes to the examination system, and how rich families would rise by marrying a daughter to a holder of an examination decree. How Confucianism, Daoism, and Buddhism changed and reacted to each other. And more.