"Farthing" was her first science fiction novel. It was a mystery and an alternate history in which the United Kingdom made peace with Adolf Hitler before the United States entered World War II. It was nominated for a Nebula Award, a Quill Award, the John W. Campbell Memorial Award for best science fiction novel, and the Sidewise Award for Alternate History. A sequel, "Ha'penny", was published in October 2007 by Tor Books, with the final book in the trilogy, "Half a Crown," published in September 2008. "Ha'penny" won the 2008 Prometheus Award (jointly with Harry Turtledove's novel "The Gladiator") and has been nominated for the Lambda Literary Award.