Sorry, but I just finished season 1.

I thought it was very good. But I expected a lot more. It wasn't even very long. 13 episodes isn't much considering series tend to span about 24.

This was a good series - but not the best thing I've seen on TV. As I said, I enjoyed it greatly, and this isn't a critique of it or anything, but talking only about the first season - what makes it so good?