I've definitely seen that formulation in detective novels. It works for me when it feels a bit tongue in cheek, but sometimes I have the feeling that the author is holding up their own novel as a Realistic Detective Novel, not like Those Other Detective Novels - the grimdark of detective novels, if you will - in which case I roll my eyes. If I wanted realistic crime I would just read true crime!

Yes, overall it's a good book. The ending undermines the middle but doesn't totally spoil it, if that makes sense. And I could see it being quite hard to end without having Owen and Natalie get together romantically - I suppose you could just have them reunite as friends, but you'd have to fight against generations of love stories to do it.