Historical Fiction
What was your first clue? Okay, yeah, the fact that the novel is set in the early 1900s is pretty much a dead giveaway. But there's also something special at work here, a technique that gained Doctorow a lot of attention. Before this book, people were used to reading biographies (non-fiction) and historical novels that featured a famous person or two.
But Doctorow combined fact and fiction, famous and not so famous in a way that wasn't just biography or trying to re-retell a historical event. He re-created an entire time period, demonstrating the way history affects us all, and showing the way each of us is part of an intricately designed web of time in which our actions affect people in ways we couldn't have imagined.