App to edit iBook author file on iPad

Dear all

I'm trying to create a book using iBook author on my Mac. However, while I'm traveling, I would like to have the ability to continue writing the book on my iPad Pro. Is there an app for that? (I couldn't find any!)

If not, is there an alternative app, which has both desktop and ipad versions and allow cloud access to the same file?

Thank you very much

Regards,

Simon