What does the "Matter Prefatory" included in the opening of the book help the reader understand in the novel, The Lynchers?

The "Matter Prefatory" at the beginning of the book lists example after example of the violence visited upon black people in America by whites. This factual material evokes anger and frustration and helps the reader understand the motivation underlying the fictional plan. By intertwining fiction and reality, Wideman broadens the scope of the novel: this is not only a story of four men but of a race, and the collective history is as real as the individual manifestation.