Dickens is one of the first authors of his time to effectively make readers aware of poverty. He does this, mainly, through the stark contrast between his two main characters: Ebeneezer Scrooge and Bob Cratchit. He also uses characterization to evoke a strong emotional connection to the characters, which further emphasizes the idea of wealth versus poverty.
In the short book, the audience is invited directly into the homes of both Scrooge and Cratchit. While Cratchit slaves away for a meager earning and is barely able to feed his family, we still see a table full of hope, and a family that is clearly full of love. In contrast, Scrooge's house is large and lavish, but he is an angry, lonely, and selfish old man.
At a time when most authors themselves were not poor, it is to his credit that Dickens was able to make such a social class distinction and speak such a social (and political) message without major criticism. In fact, because of his character development, he is able to evoke both pity and a sense of triumph for the poor Cratchits, but also for rich Scrooge. It is through contrast and emotional connection that Dickens is successful portraying the theme of poverty.