Change can be a positive thing
One of the most important themes in The Best Christmas Pageant Ever is that change be a positive thing. In the novel, the town has put on a Christmas pageant every year. And every year, the same people put on the pageant and the same people act in the pageant. As a result, each year's pageant is stale and boring and not especially meaningful. However, when the children from the Herdman family decided to throw their hat in the ring and act in the play themselves, things took a turn for the better (much to the shock of many people in the town). The change from more of the same to the Herdman children, although initially unwanted, is positive. Their performance is marvelous and teaches the town the true nature of Christmas, the history of the holiday, and more about the people in the town.
Religion
Religion is another significant theme in the novel. Initially, the Herdman children never attend — nor even consider attending — church. They are also not particularly religious. Although they are not religious at the end of the novel, they use religion to advance their own interests and secondarily, the interests of those around them (in the case of the novel, performing in the play and teaching fellow townspeople about the true meaning of Christmas). Separately, Christmas is a fundamentally religious holiday. Although many say that Christmas is a time of happiness and joy, the Herdman children show that the history of Christmas is replete with heartbreak and violence and death. In doing so, the children teach the townspeople about what Christmas is truly about.
Christmas
Naturally, Christmas is a crucially important theme in the novel. First, on the surface level, the novel is set during the Christmas season. Robinson's novel is also an exploration of the history of Christmas and what the Christmas season is truly about. Ultimately, in her novel Robinson makes the point that Christmas is not the holiday that many people think it is.
