Why does Jackson spend so much time describing every detail about the box?
The box is representative of one of the central themes of the story - tradition, and the danger of unthinkingly and unquestioningly continuing traditions without considering their true ramifications. In describing the box, Jackson is exploring the nature of the village's tradition of having a lottery. She says, "the black box...had been put into use even before Old Man Warner, the oldest man in town, was born...Mr. Summers spoke frequently...about making a new box, but no one liked to upset...tradition...the present box had been made with some pieces of the box that had preceded it...constructed when the first people settled down to make a village here...the...box grew shabbier each year...it was...splintered badly along one side...faded...stained". If the box represents the lottery tradition, then it has been around for a long time, is in need of reevaluation, but no one gets around to, or dares, to really look at it or change it.
The condition of the box is important--it's neglected, needs to be reexamined and fixed, but no one takes the time to do it--but also of importance is the color. The box is black. Black is symbolic of the evil within human nature which is also a major theme in this story. Other towns are getting rid of the lottery, they have examined themselves and decided that this tradition is no longer who they want to be or what they want to say about their town. The resistance of the town where the lottery is still held is largely because they enjoy taking part in the lottery itself--hence her son throwing the first stone and taking the first steps in killing her.
In addition to the historical significance of that box in the village, this is how Jackson builds suspense. As a reader, you aren't expecting to read this much detail about something as mundane as a box. You begin to wonder why this box is so important. As it turns out, that box is really the focal point of the story.
The box is the central figure of the cruel ritual followed blindly in the village. The condition of the box is shabby as the ritual itself. People dont give attention on the appearance of the box means that they are not fully loyal to their ritual but only do it to avoid hard times or do it to enjoy themselves. writer tells the condition of the box in so much detail because she wants to enhance our curiousity level, a thing described in so much detail should have significance in the story but we feel disgust in our heart for the ritual with reference to the box.
A box closed from all sides also symbolizes narrow mindedness of the people.