Note: I am not very familiar with the genre.
This is a noir book, but does not have the ‘classic’ structure I would expect: first person, unreliable narrator, we are inside the main character’s head. In the Maltese falcon every single piece of the book is from the perspective of an invisible watcher following Spade around. We never see inside the head of the characters, instead we get to know the characters entirely through the descriptions of their behavior, their dialogue, how they interact with the world. The dialogue and descriptions are full of gems, and the ending is sufficiently unhappy. Brilliant book.