Thank you for the kind word, but unfortunately there's no straightforward way to change the shadows in the RadBook. You can try to edit the default template of the RadBookItems and add new shadows but this won't be very easy.
I've attached a sample project which shows how you can add some more shadows so could you please examine it and see if it helps you?
As for you last two questions - no, we don't use hardware acceleration during flipping and I'm not sure what exactly do you mean by flickering but I guess that the text may not look very good because of the transformations that are applied.
If you have more questions don't hesitate to ask.
All the best,
the Telerik team
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