How to add a shortcut to an individual iBook file to the iPad home screen?
Host your epub somewhere, preferable direct link to open the epub itself. Eg. https://epub-samples.googlecode.com/files/mymedia_lite-20130621.epub
From the address bar, select the Share icon and add it to Home Screen, rename it to your epub name.


When they open the URL, they'll see options to open epub in supported app, with Open in iBooks on the right button.

The first time they open the epub, it'll be imported to iBooks, open them in iBooks. After that, choosing the same option will open the same epub, preventing duplicate.