Thanks :)
You should probably take a look at your screen brightness, the black levels are a bit varied (particularly around the THX and Lucasfilm logos at the bottom of the spine).
I've had the same trouble myself (with my first mainly-black cover), so I know what a PitA it is to fix. If you're using Photoshop you could just try using 'levels' to squeeze down the blacks to a consistent tone, if you follow my meaning.