Bob Le Flambeur was almost perfectly summed up by Melville himself when he called it a "comedy of manners" (http://www.sensesofcinema.com/contents/cteq/03/25/bob_le_flambeur.html#1). Although there are certainly some comedic elements in the movie, comedy in this case more accurately means a contradiction. The appearance and the reality of Bob's life are at odds, both in the context of the movie and the eyes of the viewers.
As Bob is a shrewd and well put-together person outwardly, so is the film's style. The camera does not draw attention to itself as it does in many other New Wave productions. The use of the hand camera, natural lighting, and transition gives this film a very natural feel. The evidence of Melville being a precursor and huge influence to the new wave is very abundant throughout the film.
Although the film is shot in a tight and modest way, its main character is anything but modest. Bob simply lives in a different reality than the other characters. He holds morals uncommon of the pre-conceived gangster, and comes out on top despite everyone around him falling. His unnatural luck in the gambling scene at the end of the movie contrasts very starkly with the fate that befalls the other gangsters. Perhaps Melville is commenting on the importance of honor and manners by saving Bob from the pre-ordained failure of the heist. Bob is not a common criminal, and he does suffer the consequences of one.
Another comment worthy feature of the film is the lack of a real villain. Only Marcus is painted in any real negative light. Whether crime is glamorized in this film is open to interpretation, but Melville certainly follows the American style of gangsters one can sympathize with. At the same time, however, it is not through crime that Bob is able to prosper, although he would if he could get away with it. The reality of the movie, however, is that he cannot suceed. It is clear to the police from the beginning of the heist planning that Bob is up to something, and his reputation allows for nothing less.