The latest edition, 2019, of the standard Korean language stamp catalogue has been published. This catalogue, internationally known as the Korean Postage Stamp Catalogue (KPSC) and in Korea as 대한민국우표가격도록, is the most specialized catalogue about stamps issued by the Republic of Korea.
As was the case in previous recent editions the KPSC contains both the postage stamps of the Korean Kingdom/Empire period (1884-1905) and the Republic of Korea (1945 up until Q2 2018). Besides the postage stamps other specialties include many types of postal cards and aerogrammes plus the Christmas seals and (national) revenue stamps.
The catalogue is available on either Ebay (search for “Korean Postage Stamp Catalogue”) or, if you can read/write Korean and have a Korea bank account, Kobay (search for “대한민국우표가격도록”). A good grasp of the Korean language is useful in any case as the text in the catalogue is (understandably) almost exclusively Korean.
To give an idea of the catalogue here is some original artwork from the lay-out files as put online by sellers on Ebay and Kobay:
Copyright (graphics): (사)한국우표상협회 / 창간호