Uploading your book to Dropbox’s free cloud storage is a really quick way to share your book with your friends, family or students.
1. Install Dropbox on your iPad
To get started first install the free Dropbox app onto your iPad, and create an account with Dropbox.
2. Export your book from Book Creator to Dropbox
Once the app is installed you’ll see “Open in Dropbox” appear in your list of export options (in the toolbar in the top right of the menu bar, or below the book in the 'My Books' view.
3. Save the book in Dropbox
Tap Save and wait for the book to upload to Dropbox (this might take a while - depending on your internet speed and the size of the book). You're now free to share it with anyone else. Tap the export icon in the top right and you can share the book - the easiest way is to Copy the Link and paste the link into an email.
And the best bit about it – the people you share with don’t need to be Dropbox users. They can just tap on the link and open your book straight into their iBooks app.
If “Open in Dropbox” doesn’t appear in Book Creator after installing the Dropbox app then check if there are already 10 apps listed in the “Open in another App” section. The iPad will only display up to 10 apps in this list, so you may need to uninstall some of the other apps listed before Dropbox appears.
About the "No Preview Available" message
A lot of people are deterred by the fact that they see this message when trying to open a book in Dropbox (in previous versions of Dropbox it said "Couldn't Load File").
This is nothing to worry about. The reason Dropbox gives this message is because it cannot display an ePub file within the app (unlike PDFs or images, for example, which will be previewed in-app).
This does not mean you cannot open the book in another app, just tap the export icon and open in iBooks or Book Creator.
From the blog: