I started watching this drama because it's my favorite genre combo - I love thriller + romance/rom-com combo and I watched quite a few of dramas like that. I may be biased but I'll try my best not to. P.S. English is not my native language, so I'm sorry if there are some errors. Also that's my first review I hope it's helpful.

STORY:
I read few reviews and I can see not everyone liked the story. I get it, it's different from most of k-dramas (especially those categorized as rom-coms) because the ending may seem unfair, sad or like for me bitter-sweet. However, that's what I like the most about this series; creators weren't afraid of breaking the (for the lack of the better word) "rules" of making certain type of drama and that may not please most of the fans, but it certainly adds depth, suspense and shock to the story, well, at least for me. That's why I like it, the story gave me some fuzzy feelings with romance and all, but more importantly it gave me what most of the dramas doesn't shock, frustration (the good kind of one) and heartache.
I do however, have some reservations or objections. It may feel like this drama is not sure what it wants to be, the first part of this series is mainly romance whilst the second is much more centered around the thriller narrative. This may create a feeling of dissonance in the story and could have been easily avoided if only there was more mixing between the two parts. There is also the problem of pacing - I feel like the narrative is running like crazy in some episodes and then it's slow and lazy in others and I'm not sure if I like it. Finally, there is the amount of long-winded, all-talking scenes which for me could have been shorter or shot in other, more interesting way, but it may be just me and my short span of attention.

ACTING:
Acting in this series was exceptionally good, Park Jin Young and Shin Ye Eun have really nice chemistry and both of them have the abilities to show a wide range of emotions without me feeling like some of them are faked. As for Kim Kwon at first I wasn't sure about him, something about his acting method rubbed me the wrong way, but after ending the series I must say he portrayed his character very well. Although I must admit that the person who stole all the scenes for me was Kim Da Som - my eyes drifted to her every time she was on the screen.

MUSIC:
There is not much to say about the music here. I liked the OST it's nice but I feel like it didn't match the story. Regarding the music in scenes this drama tends to be more silent than most of the series in this genre category (e.g. Strong Woman Do Bong Soon).

REWATCH VALUE:
Well, I don't see much rewatch value here, but let's be fair most of us rewatches series that we love, so perhaps you'll find it (granted it'll become your fave).

OVERALL:
I liked the drama. I liked that it played with my emotions, but it's not for everyone and you should know that if you're looking for sweet ending like for instance Do Bong Soon, that I mentioned earlier, this is not the one - keep looking, but if you don't mind bitter-sweet one give it a try!