And how do you implement this book-page turning GUI? I would be interested to hear that... If not confindential, of course :-)
Hi, thanks for your interest.

I took an empty game object as parent and added two sprites to it, one of it rotated by 180° so it acts as backside. Then I just animate the parent. The turning page isn't perfect as it doesn't bend, but sufficient enough.
Meanwhile our game is actually finished. It's called "Reperfection". There's also a demo (at tinnitus-games.de) if you want to take a look at how I implemented the sprites as a book.
Best regards,
Cales