Is The Big Sleep classic influential film noir? Absolutely. But vastly more than it deserves because it's an inferior Maltese Falcon polluted by a campaign intended to normalize the affair of a married actor in his mid-forties with a girl just out of her teens.
Raymond Chandler's novel The Big Sleep, published in 1939, elevates pulp detective fiction into a classic of American lit--ten years after Dashiell Hammett did it first with The Maltese Falcon. But the movie isn't Chandler's book.
John Huston's 1941 Falcon is visually and thematically darker--more noir--with striking use of shadows, better use of music, and unforgettable dysfunctional characters--notably Sidney Greenstreet and Peter Lorre.
If Humphrey Bogart as detective Philip Marlowe seems slightly similar to Humphrey Bogart as detective Sam Spade it's because he plays them just the same. And whereas The Maltese Falcon concerns the obsessive quest for a fabulous prize, a dark object which can be held, The Big Sleep has a guy being blackmailed. Right there, comparison-wise there is none. First one interesting, second one not so interesting.
Makes better parody material.
Yes, the Coen Brothers saw The Big Sleep. One can even hear their brotherly quips and comments while watching it together. Let's listen:
"Say mac, what if it wasn't Bogie in the story, but instead our L.A. hippie buddy? Might that not amuse?"
"Plus there's a rug in that one scene. That's what our L.A. hippie buddy would have to deal with. He'd be bummed that it got stained."
"But we couldn't call it The Big Sleep."
"You're right. We'd have to call it The Big Lebowski."
Two years prior to Sleep, Humphrey Bogart met Lauren Bacall. He was 44, she was 19. This was on the set of Howard Hawks' To Have and Have Not. For that one, the studio paid William Faulkner to adapt Ernest Hemingway's novel. So they repeated that formula as best they could a few years later by having Faulkner adapt Chandler.
(In the Coen Brothers' Barton Fink, John Mahoney plays Faulkner around this time, very much depressed at having sort of sold out.)
The private lives of the stars off-screen need not have been dragged into the film, but protecting the commodity was how the studio system worked at the time. The filmmakers conducted a four-pronged attack in defense of established moneymaker Bogie:
1. They effectively reduce his age by eight years when Marlowe says he's 38.
2. They effectively raise Bacall's age by giving her a much less mature younger sister.
3. They make all young women in the film instantly sexually aggressive toward Bogie, thereby normalizing his being paired with someone less than half his age.
4. They sanction the pairing, advertising it as "incendiary chemistry."
None of which would impair the film, except it's done in lieu of action. And that's the eye-opener. The willingness to put public perception toward a relationship the bare facts of which most people would find immediately distasteful ahead of the action in a story.