In Cold Blood: A True Account of a Multiple Murder and Its Consequences by Truman Capote
This is an extensive study of the 1959 murder of a family in remote Kansas. It compares the lives of the killers with those of the victims continuing through the trial and execution. It can be seen as a non-fiction novel. However, one central character is missing from the story: Capote himself. He inserted himself in the sequence of events from after the killing through to the execution becoming far from a dispassionate observer.
I read this after seeing the Capote film for the second time.