So I'm gonna make it short and simple
I usually don't watch this kind of stuff. The kind of drama that includes only police, crime with very little romance is REALLY not my type : i'm not afraid to say it but I'm more into cheesy romance. It's not that I think that police and crime dramas are not good but I'm the type who watches dramas to cheer myself up from a boring reality, not to watch the harsh problems of reality.
But guess what ? Even I liked it. Even acknowledge the quality of this drama. I watched it initially to see Lin Bo Yang again, that I hadn't seen much since Blood of Youth, despite liking her very much.
But I still find myself sucking into, expecting next episode, being interested by the themes and the various characters.
Fighting scenes ? Awesome, not too present so they're obviously not here to compensate a lacking writing
We don't have just investigations about various but the characters have all their personal stories, with distinct personalities and psychologies. We see how their backgrounds intertwine with the cases and this is heartgrasping '(lol, i just invented a new word). We're touched with them, worried with them, and when they get into difficult situations, our heart breaks for them
There's never a dull moment. We always get some new event, new revelation, making us hold our breath, with a sense of mystery floating above all of this
Therefore, the writers succeeded into making this not only a story about crime and investigations but also about the human being and his psyche, and human relationships
And I think the best part about the writing is that it shows how think the line between bad and good can be : the "villains" or aren't stereotypical, one dimensional characters and criminals. Many of them found themselves sucked up into the underworld and therefore have no way to get out of it, as it is part of them now. They're not part of it because they wanted to or because they were greedy and they're not necessarily evil. I'd say the most striking example would be Jiang Xiaohai, who, despite first appearing as being of little importance, also became the most remarkable character of the show (great applaud to the actor's performance), as it was sometimes very unclear how much he was involved in all those crimes and conspiracies and yet, very often, he appeared as someone with principles

Edit : however, there is a thing that bothers. There is a character at the end to whom they did REALLY dirty by not even giving him a proper ending.
But I think the screenwriters were somehow trying to show some realism so I’ll let that pass. Nevertheless this felt both heartbreaking and frustrating, which makes me take out just one little half-point
So in short : really, even if you're not into this, give it a try for at least the first episodes. Just like I said, even I liked it