Perfection.
Firstly, the writing. Each of the characters is so intricately woven, their traits so strongly written. You are constantly finding something new to admire in these characters, and by the time the series ends, you have fallen in love with all of them.
The cinematography in the drama is extremely beautiful. The set, lighting, locations, all tailored to capture the emotions in the scene perfectly.
And of course, I have nothing to say about the acting. Each actor did incredible justice to their characters.
Overall, this is a solid series to watch.