Liz Castro created a
Manga sample epub3 with an
com.apple.ibooks.display-options.xml file in the
META-INF folder that opens fine with Readium.
Most likely there's something wrong with your
com.apple.ibooks.display-options.xml file. Did you make sure that it's syntactically valid and did you save it as an UTF-8 file without a byte order mark (BOM) and no line breaks after the last line?