Because it's KyoAni. Simple.
Art is absolutely gorgeous, but that's something we've already come to expect from KyoAni. In addition, you can see KyoAni try new things such as the stylized mystery sequences and the watercolor painting. I already eagerly await the OST, and the occasional use of classical music is more than welcome. I really like the atmosphere of this series too in general, but then again I really liked K-ON and I understand that to some people, this art style is a turn-off.
I don't expect any serious mysteries from this series, but that doesn't mean this is going to be anything as boring as Kami-sama no Memochou, KyoAni today is about the characters, and is a full-fledged high-quality production studio of B-Type series. Coming into this series expecting any form of real mystery will undoubtedly end in disappointment, looking at the resolutions of the mystery elements of this first episode, but that's not what you look for KyoAni to do. I'm glad to see that KyoAni is doing what they're best at in this series, and they're not trying to be a studio they're not. I know the K-ON haters will bash this show as well, citing the same reasons as they did for K-ON, but they just don't really get the appeal of KyoAni's works.
I'm eagerly awaiting the next episode. In fact, much more so than Fate/zero's next episode, if that says anything about how much I enjoyed this series thus far.