I can se how this would put some ppl off, as it breaks away from the "traditional" cover styles.
Me, I think it's acceptable, I mean this is a book about strategy, not one on say Background Fluff or More Feats Than I Can Fit In My Pie Hole.
If I hadn't seen the cover thumbnail, I probably wouldn't have even bothered taking a closer look.
Considering the sort of MMO feel of 4th Ed, I kind of get spirit of this cover and (if indeed the interior art is similar) the content art too. If anything this would probably make ME (yes, ME) MORE inclined to get it, as I am a fan of that kind of Star Wars Clone Wars/Samurai Jack style of art.