This drama got me hooked since day one, and there are various reasons for it:
1) Amazing plot - The plot is completely new,at least for me. The story has developed very well and at also the right pace. It is one of the kinds where you'll probably die out of curiosity trying to imagine what the next episode would be like. I laud the person/people who came with such a story.
2) Remarkable actors - Son Ye Jin was the reason why I started this. But now Hyun Bin has me wrapped around his finger. Seo Ji Hye and Kim Jung Hyun are also brilliant. Everyone's acting is so good, that it feels the roles were written for them.
3) The chemistry between the characters - This is also one of the reasons why I waited for the drama so patiently every week. The chemistry is so good and it makes me ship them way too much.
4) Supporting Cast - The supporting cast has done a splendid job, in fact the entire cast. The scenes involving them have been written really well, you don't wanna skip any scene. Kudos y'all!!!
5) OSTs -I love each and every one of them and I can't help but listen to them all the time. They're all very good!!

All I have to say is, if you're looking a unique story with amazing actors wrapped up together with soothing OSTs, you should most definitely give this a try. :)