This is a weird book, published primarily in Singapore, and somehow not fitting the canons of what people “are supposed to do” (NB: it is not at all racist, just bolder in its cultural generalizations than is currently in vogue). Nonetheless I learned a great deal from the book, while taking some parts with a grain of salt. Here is one interesting bit of many:
Since 1948 the government in North Korea has been dominated by people from North Hamkyong Province, where the late Il Sung Kim, founder of the North Korean regime, was active as a guerrilla leader during World War II. Since that time people from the North Korean provinces of Hwanghae and Kangwon, which are the closest to South Korea, have been virtually banned from high government offices because they are considered untrustworthy and unfit. In South Korea government has been controlled mostly by natives from North Kyongsang Province in the Youngnam (formerly Shilla) region.
…Ongoing competition and conflicts between people from Cholla and Kyongsang Provinces are said to be serious enough that they have significant negative impact on national politics, the economy, and life in general.
The author is Boye Lafayette de Mente, and he seems to know a lot about Korean bowing. Do note the book is mainly about South Korea. Reviewers, by the way, complain that there are significant mistakes in the Korean characters. Recommended nonetheless, albeit with caveats, you can buy it here.