I just published a free book for the iBooks library using iBooks Author and iTunes Producer. While it was not the easiest thing to do, it was fun and what a great tool for digital storytelling classes everywhere. My book is ACT - the art of going everywhere without going anywhere - Green Screening.
I will publish follow-ups and teachers all over should publish lessons to share. My 1st book is located at:
and also available in the iTunes Book Store
I have since published additional chroma lessons and while the first was not very easy, the process is far easier than creating an app. The book creation is similar to creating a Keynote with interactive slides. The publishing end is a little more difficult. You have to not only save a published version from iBooks Author, but you also have to export it. Using the iTunes Producer is straight-forward. You must create an account to publish with iTunes Connect before publishing any book.
My publications are available on the iBookstore.
Pleae let me know if I can be of any help.