A couple of people have asked how they can make unrealBook display white on black instead of black on a white page. Turns out it's built into the OS. Run the Settings app and go to General->Accessibility->White on Black to ON. This will display white notes on a black page.
It also makes the iPad look "interesting".
Version 2.5 has an amber mode setting for night use. It's in settings->globals->view->Use Amber tint.