I've just made a .ibooks file, and if you unzip it it's just a normal epub3 file (I think). The mime type is application/x-ibooks+zip. If it's not epub (not 10

I've just made a .ibooks file, and if you unzip it it's just a normal epub3 file (I think). The mime type is application/x-ibooks+zip. If it's not epub (not 100% familiar with format), it's just xhtml, css, svg, some plists and all your assets (jpgs, pngs, etc)