Quite possibly what is known as one of the top crime detective manga out there.

Ouroboros is filled with a diverse character list and clashing motives. When people have such huge motives, what will happen when someone goes against them?

The story is a long string of complexities, all of which have their small branching stories and interesting moments. Each character gets time to show what they believe in, and justify their way of living before it is compared to another character's, and the climax is seeing who's justification for being alive was better.

The art is always clean and allows each character to look distinct. Thugs with little to no reason for living all are identifiable while characters who have a strong desire to live are imposing. This manga intentionally lets you spot the main characters without strictly making their appearance different.

The characters are very complex and have motivations and reasoning for the things they do. Nobody does anything which isn't explained. Characters bounce off of each other and seeing how they react to each other (which is usually in a hostile manner) is extremely suspenseful and interesting.

This manga is definitely enjoyable as a crime detective manga.
However, I would agree in how people who don't like the genre of crime/detective might not like this manga. This manga stays true to it's genre, and when it tries to branch out to a more romance genre, it's noticeable on how it doesn't compare.
The ending was a little short-lived in peoples minds, but it was still a good conclusion to the series. I wouldn't find myself rereading this manga, however I will say that this is one of the top thriller crime mangas I've read.