Think about the subject matter to start – we have a nameless, broke protagonist trying desperately to save the woman he loves. It would be difficult to take any kind of tone other than sadness with this story.
At the same time, however, the protagonist's descent into madness represents a kind of transcendent hope. He forsakes his old, beat-down, suffering self and is reborn as the King of the Bingo, someone who controls his own destiny. However, his reign ends rapidly, leaving us right where we started: sad.