I recently read through the sound novels and was very impressed. Great music, and the story keeps making me create theories, many of which are probably wrong.
So far, the anime has been average in how it's adapted the material: a lot of the cuts I can understand for time reasons, but because of this a lot of scenes lose their oomph. (such as the third teaparty) Overall, the sound novel felt more powerful to me and thus better, as it had time to go into detail. Also, I think the music helped set a very good atmosphere.
However, I found that some parts dragged on a bit, like the beginning of 1(which does make sense, having to introduce characters...). Also, the art is a bit...funny-looking at times, but some of the expressions manage to be pretty creepy. They're funny-looking enough for me to shrug off everything that looks awkward in the anime. Except maybe for the MEGA-BREASTS. I mean, seriously, because of that I couldn't stop laughing in that classroom scene in episode 21. That and the fact that Lucifer, uh, 'died' twice?