How to get self made iBooks onto supervised iPads?

We have a number of supervised devices that we lend to staff, one of them has asked for us to place an iBook that he has made in iBooks Author onto the devices.

Helpfully, iBooks doesn't support iTunes file sharing so we can't assign the iBooks file to the user in Apple Configurator and drop it onto the device that way, so I thought I would just upload it to Dropbox, download it on iPad 1, open it in iBooks, back up the device and restore it to the iPads that need to have the iBook.

I did it and although when I opened iBooks on the 2nd iPad it showed the icon for the book it disappeared when I clicked on it, like it was there but it wouldn't let me access it once I clicked on it. It does this on all of the iPads I restored the backup to.

Is there a easy way to get self made iBooks content onto multiple supervised devices?