My reasons for seeing this series came from its writer and lead role actors (Son Ye Jin and Hyun Bin) and I was sure it would be a good series.
The awesome story and great acting of the actors, both the lead role and the other actors, made this series one of the best I've ever seen. It should be noted that its delicate and beautiful Ost adds to the charm of the scenes. The story line throughout the episodes was so engaging and exciting that made it difficult to wait for the next episode, and I wanted to see the next episode immediately.
To put it in a sentence, this series is so spectacular that is worth watching over and over again.