I've noticed that whenever I have to use the dictionary or click something on the menu (like adjusting screen brightness), the text becomes uneven (some parts darker, some parts lighter) when I return to my book.
To demonstrate, here's a picture of my screen with the brightness adjustment menu over the text of my book:
When I exit the screen adjustment menu, notice how the text enclosed in the red box is bolder than the text outside it -- coincidentally the part where the brightness adjustment menu used to be.
Same image, without the red box:
And after refreshing the page (turning one page back, then forward again), everything is even again:
This is just a minor annoyance and quickly resolved with a screen refresh, but I just wonder if this is normal with all PW's? I have screen refresh set to "on" by the way.