It happens sometimes that the beauty and the talent of an actor stands out more than the story in itself. I've seen other movies and dramas with Ah-In Yoo and it didn't happen but this time I got distracted from the story many times just by looking at him. Maybe the make up and the good clothes. Of course, he is a brilliant actor as well. I strongly reccomend Burning to see a more indie side of him.
I agree with the other reviewer who said that the chemistry between the two main characters was better in the past than in the present.
But, all in all, it is a good drama, original, unpredictable and full of suspense, with smooth transitions from present to past.