what do you think is the central theme of the story

There are a few main themes that you might consider. Certainly the theme of tradition and custom is at the forefront. Initially, the lottery seems to be a vital part of the new harvest year. It seems like a tradition familiar to all the villagers. Throughout the story there are hints that this tradition has a darker meaning. Most of the trappings of this tradition have been lost or neglected over time. All that is left is the morbid conclusion of the story. The Lottery becomes tradition for its own sake, which appeals to the darker forces of human nature.