Personally, I like the second cover better, mostly on color... the first one looks really dark.
The only minor nitpick I can see is that the sharp angle on the cloak is leading the eye off the page and not back on the page... but that might be expensive to fix since you aren't the artist.
In order to fix that either angle it *in* so that the eye is lead up or do a slight curve on the cloak.
Picking on it because in my graphic design classes and drawing class I was told to compose so that the eye keeps moving in the drawing plane. When the eye is forced off (for no good reason) the eye stops seeing details. (Just in case you need to know why)
But that's really a nitpick.
And a minor other note, the warm colors are nice, but a minor splash of blue would anchor the color scheme into triadic... unless you're going analogous (so then anchoring it with a saturated orange might be nice)... (I tend to like contrast colors of cool and warm) though that, too, is really a nitpick too.