I've been reading a lot of Victorian novels in the last few years. Slowly it is has dawned on me that the subject matter of most Victorian novels can be algebraically reduced to two main topics: Money and Marriage. All the characters' ideas, efforts, and conversation tend toward these two things, either as future goals or as present problems.
To be sure, another common theme may be the keeping of guilty secrets—but those mostly have to do with money and/or marriage. Another frequent theme is religious piety—but mainly as it impacts, or is impacted by, money and/or marriage. Crime and the solving of crimes can often be seen as a theme in these novels—but can you guess the usual motives for such crimes? Also, admittedly, a lot of Victorian novels go in strongly for social reform—but almost all social reform is at least indirectly related to money, and what little is left may be considered relevant to marriage.
And besides... Most of the melodrama relating to marriage is based on concerns about money. People who want to get married are prevented by the lack of money, or by disparities of income and property, or by social mores that disapprove of marriage regardless of these concerns. Matrimonial prospects are evaluated in the light of the money they will bring to the union. Marital happiness or strife will be measured by the degree to which the couple is well-matched in their handling of money matters. Adventurers go about deceiving marriageable women with the same hue of mendacity with which embezzlers, spongers, and grifters grasp after the funds of others. Horrors of villainy and revenge have as their target either the innocence of eligible daughters or the disposition of wealth and property.
So, in a crassly simplistic sense, the 19th century novel is pretty much all about money, with marriage often added as a sugary coating to help it go down.