First episode is very solid, 10/10. This is exactly what I had hoped to see in the main series. Shiki would've been so much better if it was like this throughout the anime. It focuses on the characterisation of Nao. The second episode is not as good, I feel like it would've been much better if everything was fleshed out over 2 episodes. There were some holes in the story because things happened too fast. Still, it does explain things that happened in the main series. Also fleshes out a character(well, 2 I guess). I'd say 7/10 for that. As a whole,I'd say this is an 8.5.

Beyond this, not much needs to be said. If you're a fan of shiki, you'll want to watch this.