A seemingly naive young woman from rural Middle America hires Marlowe to find her brother, who moved to LA to see the lights and hasn't been heard of in months. As with every Marlowe case, this initially simple proposition blossoms into a labyrinth of corruption, blackmail, and murder in which almost no one is what she or he appears to be.
Chandler's style was so influential that it permeated hardboiled detective fiction, as he added a level of pungent description and social criticism to the prior pinnacle of hard-boiled fiction (and still influential and excellent, then-and-now), Dashiell Hammett and his detective Sam Spade.
Both characters were played by Humphrey Bogart, appropriately and memorably, in movies: Sam Spade in The Maltese Falcon and Philip Marlowe in The Big Sleep. An odd but enjoyable movie version of The Little Sister was made in the 1960's with James 'Jim Rockford' Garner as Marlowe.
The Little Sister moves fast and tight, plot-packed without neglecting Chandler's strengths, deployed through first-person narrator Marlowe, at character study and subtly metaphoric descriptions of the California setting. Highly recommended.