Visualizations are not just for social scientists with data on their hands. They can be used to analyze literature too. After all, most fiction writing is writing about social relationships. Take this example from a Shakespeare play (click on the image or here for the full thing):
You can clearly see where the big drama / plot points are, the messier entanglements between acts 2 and 3, and the resolutions in act 5 (compare where the lines start in act 1 and the different groupings at the end of act 5).
This is not the only representation one could envision. Relationships are of different nature: conflict, cooperation, competition, etc. That could be visualized too. One could also group characters into set based on common characteristics, such as family, religion, social class, etc. I really like the idea of mapping literature work that way. I might actually try once I get more technical know-how.