IBooks background on opening

I believe that is related to daylight/night time light conditions. It will open to a white background in light and it opens to a black background when you are in dark conditions.

You can set it to a white background while reading by tapping the two A’s in the upper right corner and select Auto Night theme>Off.

Maybe you have a funky pdf or bad download causing problems.

Did you try what I suggested? If you did and it don’t help, close iBooks again from the app switcher and force restart your iPad. To force restart your device, press and hold both the Sleep/Wake and Home buttons for at least ten seconds, until you see the Apple logo.

Did you check that setting that I spoke about above? Make sure that is turned off. Close iBooks completely and launch it again in a well lit room.

Excellent. I’m glad it worked for you.