Dare I ask did you again forget to select the correct paper type?
Also my printer has two settings that factor to the end result (and ink consumption):
First is the paper type (matte, normal, semi gloss, glossy, extra gloss...) the second is print quality (low, normal, high quality, photo...)
You can try to select higher level paper than your using.
But I have to admit, not all the covers here are high quality, few are pretty s***, like NES Adventure Island 2's front.