I completely agree with you on the therapist (because he said my patient is the real killer and probably doesn't think Alex stories about those murders are delusions! )
but the detective's motive/( sanity) is very questionable! He seems to be fascinated by death and murder,maybe he really doesn't want to publish and is after something else! He seems to be searching for something that even he doesn't know but has everything to do with death and those who commit murder!
The premise puts me off too. It does require a huge suspension of disbelief. I had hoped that this would be another psychological thriller but I don't get the usual thriller vibes from it. I guess it isn't because it doesn't say so in the genre (however, the tags say it is).
The Mc's hobby is collecting the dirty, dark and sordid secrets of people, and keeping them to himself. We also saw him seem unaffected by the kitten's death as a young boy. It's hinted that the has his own dark side, he may even be a psychopathy, he definitely doesn't seem any better than the killer.
His journalist status permits him to partake in his hobby, considering he gets informants thanks to the subjects his "covers" (although he seems to drop some when he gets the secret for himself).
So with all this slowly revealed, it doesn't seem that weird that he doesn't go to the police, he's not concerned with justice. I'ms sure he doesn't even intend to publish his story, he's too captivated by its darkness. He'll do like he did with the other stories : keep it in his library.
The psychologist, as a mentally sane person, should indeed have told the police. BUT, he seems to have a hero complexe, he keeps talking about how the ML is fragile and may get hurt because of Mc. I think he got manipulated by ml into thinking he's someone he must help + he seems to have developed a crush on ml. Considering he is Mc's ex, and knows of Mc's hobby, he has questionable taste in men, with an unhealthy dose of delusion of being able to save Ml from whatever mental illness afflicts him.
so that keeps bugging me every time I read it. It keeps taking me out of the story. like noo...! dictionaries exist/google is a thing. it could have been the triad murder, the trinity murders.
a therapist that would hide the fact that he suspects his patient...is he okay if the guy eventually kills more people? And the reporter, if/when he published the killer's story he could go to jail for not going to the police with the info first. (aiding and abetting)
so while I read this am I just supposed to suspend all disbelief...?