Neither Thrilling nor Noir
Pretty sure I saw this in the 70's, though I can't remember what I thought of it then. Now it seems tired and uninteresting. Start is very slow setting the scene with Marlowe (Elliot Gould) who doesn't appear to be a working private eye, more a loser who talks to his cat. A long drawn out joke about cat food hardly tells us anything about the character (although our dog watched it intently).
Once the story begins it moves along ok, although the threads are initially disconnected there is no sense of mystery or confusion which one might expect from the classic Chandler films -Leigh Brackett who wrote the screenplay was also co-writer of The Big Sleep (1946) but was way off the mark here.
The wisecracking by Marlowe doesn't sparkle - perhaps because there isn't a female co-lead to spark off, so his foils are indifferent. The main women (the writer's wife and the gangster's moll) are merely long haired west coast stepford wives with no character.
The writer, a Hemmingway type, Roger Wade (Sterling Hayden) doesn't carry the heavyweight drunk role well - he is too soft. The creepy doctor Verringer (Henry Gibson) is simply a creepy nerd with no menace or indication that he might have any power over Wade.
The shooting at the end is a surprise, but packs no punch as Marlowe didn't seem to have any difficulty tracking down his friend or any particular reason to act as he did - it was neither moral nor justified.
All in all it's not even worth 3 stars, never minfd the 4 I thought I might give it immediately after, so I'm downgrading it to 2.