Many countries have established eBook standards adequate to their environments. In USA, OEB PS is announced for distribution and display of eBooks, in Japan, JepaX is announced for storage and exchange, and in Korea, EBKS is made for clear exchange of eBook contents. These diverse objectives of standards lead to different content structures, and differences of content structure will cause a problem in exchanging them. To correctly exchange eBook contents, the content structure should be considered. So, in this paper, we study content conversion of standard eBooks based on Korean eBook standard, with contemplating content structures. To convert contents properly, the mapping relations should be clearly defined. For this, we consider standard's structure and extension mechanisms, and use a path notation and namespaces for precise description. Moreover, through analysis of each mapping relationships, we classify conversion cases into automatic, semi-automatic, and manual conversions. Finally we write up conversion scripts and experiment with them.