i dont understand how the plugin work.
I understand that is should work without itunes.....send the files direct to ibooks....
The plugin does require iTunes. With a connected iDevice, books are sent through iTunes to iBooks without keeping a copy in iTunes.
Where i find how it works?
The driver communicates with iTunes using app automation to transfer books and metadata.
If you're asking about how the plugin is implemented, the code is in calibre/devices/apple/driver.py.