Fans of hard-boiled detective fiction know what they want. Fast plotting, snappy patter, just enough violence or the threat of same to keep it interesting, and not too much of the mushy stuff.
The Maltese Falcon not only delivers on all those points, it works the template to perfection. Just reading the first two chapters awakens you to the fact that before they were tropes, such things as mysterious dames and foggy crime scenes could be so evocative and alive.
Making it all snap together is the dynamic central character of Sam Spade, a tough-talking detective with honest-to-God principles, most especially that no one’s gonna make a sap of him.