I'm currently reading this, The Radleys by Matt Haig. It's being published next month (July 2010) under two publishers in a joint publication deal. Cannongate will be publishing the adult edition, which you can see on the right, and Walker Books will be publishing the children's edition, on the left.
I really like both of these covers. I think they're both quite quirky. The blood running down the fence post on the adult edition. The red house standing out on the children's edition. The sin city feel of the children's edition is brilliant.
For me, I have to go with the children's edition. Not just because that's the one I own, but because it's the best of the two, or at least the one I prefer. It's a lot more intriguing and artistic.