An electronic book means a digital form of a paper book. Currently, to promote an eBook market, many countries have established eBook content standards. But, the publication of different caused exchanging problems due to mismatch of content forms. Therefore, to exchange eBook conforming each standard, the content has to be converted according to document structure and its semantic information. But existing conversion methods are almost based on syntax information. Even, using semantic information they are not reflected eBook characteristics. So, to precise and correct eBook conversion, we analyze each standard and define mapping relations considering semantic information and eBook characteristics. To generalize the mapping relations, we classify mapping relations into ten conversion classes, and provide conversion scripts examples for each class. With defined mapping relations and conversion classes, we write up conversion scripts for EBKS to OEB PS/JepaX, and experiment with them. We believe defined conversion classes can be applied to normal document conversions.