This is an action/murder series in which a Chinese man is reincarnated as a Caucasian Texan kid in an alternate universe. The title and synopsis are very misleading. Although "detective" is in the name, the MC has not done any investigative work at all. THIS IS NOT A MYSTERY SERIES AT ALL. On the contrary, he becomes a police officer and goes around killing people with excessive brutality. Despite this, he hasn't even been investigated, suspended, or arrested for his crimes.
Aside from his system, there are no super powers or supernatural elements at all prior to the series going premium.
There is ample racism, sexism, and nationalism from the main character. Women are weak, even if they're police officers and have not demonstrated any kinds of weakness. The Chinese always do things better and are more sensible. Why didn't the author just reincarnate him as a Chinese American, then? There are plenty of Asian people here. This is very off-putting and distracting from the plot.
The MC himself is a Gary Stu with great grades, great looks, and great abs. Although he becomes excessively violent and even executes criminals who are incapacitated, there are no legal repercussions, and he's never risked being removed from the force. Is he even human? He feels no guilt, hesitation, or remorse after killing people. He is interested in his system and is savage, but he otherwise doesn't have any emotions. No bitterness, no sorrow, no regrets, no lust, no nothing. His morality is highly questionable, too. Although he has a girlfriend he likes, he wants to replace her with a better girlfriend or even develop a harem; later, he has no interest in dating, so his personality is inconsistent in this regard. His intelligence is clearly only average, and this has left many readers facepalming in the comments, including myself.
Weirdly enough, although he was already thirty years old in his past life, he doesn't appear to have any life experiences or to reflect on his past at all. Most people would plan things different a second time in life, but he really doesn't have any interest. It feels like his past as a Chinese man only exists to give him the excuse to continue with making hurtful prejudiced comments. I'm not sure what the point is.
It's also pretty bizarre that his system doesn't punish him for breaking the law or murdering people. It's as though it was designed to make a super criminal rather than a hero, and it's abundantly obvious it's not made for a detective at this point since intelligence doesn't count for anything.
There is some characterization of other characters, but the story doesn't give them much depth before going premium.
If you are looking for another casual action/killing type of series, then you might enjoy this. If you are looking for actual mysteries, detectives, investigation of any kind, or super powers, this series does not have any of them prior to premium. I'm not going to bother paying premium here, and I don't recommend it for others either.