I have to say this film was awesome and I would love to watch it again, good dry humor and not truly plot driven (not saying the whole time I was trying to figure out who had killed his friend) and mysterious characters. I can be a stickler sometimes when a movie's plot and the events that unfold to create and solve the plot aren't very clear. But it wasn't about the murder or straight facts that you were looking to solve the crime, it was the characters' and their nature. Their current situations they were in and how they were introduced and conducted themselves throughout the movie is what drove the story. It wasn't about the cold hard facts, it was the personalities that drove themselves and lead the story of solving the crime.
In comparison to the 50s Phillip Marlowe, you couldn't talk more about water and oil. Although both fairly cunning and smooth, their approach, lifestyle, and presentation of themselves were polar opposites. the 50s Marlow was dressed to impress, while 70s Marlowe would be nicely dressed but would have cheap clothes to pull it off. And he also let people call him out on it, but still wore that JC Penny tie with pride. Like I said one was suave with his words, the other was dry, still smooth, but much more sarcastic. Both smart, but one was more of a smart-ass. I couldn't imagine while watching the 50s version of Phillip Marlow, having a slight amount of doubt that this P.I. is going to solve this crime.
I don't know if this applies, but it definitely did not go along with the "police drama formula" in which most shows or movies about police follow. Such as the movie Seven which is a prime example of this "formula".