The House of Mirth's opening chapters provide a great example of how the novel pays attention to behavioral details. In a train station, Selden carefully analyzes Lily with the intent of determining why she is there. He then plays a mind game on her, walking past her to see if she greets him or tries to hide from him. This analysis of actions is typical in the novel, as seen later on when Lily and George Dorset are assumed to be having an affair after they are seen alone together at night in a train station. And, of course, Selden becomes enraged at Lily when he sees her leaving the house of Gus Trenor late one night by herself.
The novel is built on a series of visits or social events. Indeed, most of the action in the novel happens not by coincidence but by planning. Everyone plans trips to the Bellomont knowing that they will spend their time gambling, and Lily plans all of her trips with the intent of getting something out of someone. The various visits, then, are the grounds on which all the social analyses and gossip take place. The visits are a type of societal battle-ground on which alliances are formed, people make connections, and some are judged.
The basis of much of the societal interaction is money, which serves as a prerequisite for admission to the upper-class world of the Trenors and Dorsets. The meaning of money to Lily seldom changes; if anything, her lust for money grows in intensity as she becomes poorer. What makes money interesting in this novel is the way it is tied in to ideas about freedom and slavery. Whenever Lily comes across money, she feels free. Whenever she falls into debt, she feels enslaved. But one of the great ironies of this situation is that Lily is always enslaved to money because no matter what, it is the basis for her emotions. Her attitude rests entirely on how much she can afford to spend on dresses and how much she is in debt. A great tragedy in the novel is that Lily is never really free, even when she thinks she is.
Given that money is the controlling factor in Lily's life, to what can it lead? There are essentially two possibilities in The House of Mirth (and any novel of manners): acceptance/marriage or exile/death. Perhaps the most enjoyable way to read the novel is to begin reading with the belief that the book could go either way: Lily could get married and succeed, or fail and die. In this case, it is the latter option that happens. How does Wharton work toward that end? With each chapter, particularly in Book Two, the factors of bad luck and social instability combine to slowly remove Lily from society: bad luck because Lily was with the wrong man at the wrong time in France, and social instability because Lily was not entrenched enough in society for her word to be respected over that of Bertha.
As with all novels, a logical question to ask is, "What is this author trying to say?" In the case of The House of Mirth, one answer is that Wharton wants to depict the malice and bitter realities of life in upper-class society in all its grim reality. One theme is that money can cause more problems than it solves, and one should be careful when pursuing money. Moreover, the fact remains that if Lily had followed her heart and married Selden, she would have been fine. This leads to the conclusion that one ought to be true to one's feelings, rather than play a societal game of money and power.