I summarize my review per point for you, I hope it can be useful for you who looking for review before start the drama. (The rating is exluded the music and rewatch value)

1. This drama adapted from Ding Mo's novel with the same title.

2. I suggest that you watch the drama first before read the novel.

3. You'll find some differences between the novel and the movie. Both the drama and the novel are very good.
But in the novel, it will explained more details and more to Ji bai and Xuxu relation (romance), Super sweet guys, please read it after you watch the drama.
In drama, It's more to the criminal case, and less skinship between Ji bai and Xuxu. But Wang Kai and Olivia chemistry were so good, plus Xuxu's drawing makes this drama still cute and sweet even without intense skinship.

4. The cast in drama less than in novel. And it's different character of Yao Meng. But I believe this decision was good for the drama,because of the efficiency of the drama. You will not find unnecessary scene in this drama.

5. I love Wang Kai as Ji Bai so much. He is so handsome, so cool and really suitable for the role. And Olivia even different from the Xuxu in novel but here she develop her own character as awkward, serious , and more mature. Her acting as criminal profiler also very good.

I can say this drama is really recommended and you will not feeling bored when watch it. I never skip any scenes of this drama. 21 episodes is never enough for me. Enjoy watching guys :)