Hi Jack, See if this link helps you out http://www.apple.com/itunes/content-providers/book-faq.html The Archangel
If you haven't seen it, there is a free book on the iBook Store called the IPad Publishing Guide which is probably worth a read. The Archangel
Cheers, think I am going to struggle downloading the iTunes producer as i only have a windows lap top, use iPhone and iPad, but alas no mac