Well, I don't think there will be anything above average shoujo's in here. Not that I expect any...
Two chapters in, it seems to be your run-of-the-mill shoujos, exactly like I expected when I started reading. Not unreadable, worth killing time, but there's nothing that goes above average either. You see these quite often, some girl summons or gets involved another way with a demon (king) and becomes his slave, after that she falls for the demon king and happily ever after. I dunno about the second half, but it does seem pretty accurate in this case.
The art... well, I'm probably a bit biased, but I don't think it's all that great either. But like I said, there's a high chance that there's certain amount of personal preference in there. Rui simply doesn't live up to my expectations of a demon king, much less Lucifer at that.
And of course... Meiko has your average looks, run-of-the-mill settings too. I mean that by, stupid but kind (pronounced ignorant) but annoys other girls (including me) by being together with their ideal men. Honestly... it's your typical heroine, if not boring and/or annoying.
With all that said, I'm not saying this is horrible either. It's just... average. The good thing is, it doesn't make you expect anything else other than what it can give. You won't find yourself disappointed and smashing your laptop, but neither will you find yourself crying or moved. The most this will be is funny.