Winter (The Demi-Monde #1)

The Demi-Monde is the most advanced computer simulation ever devised. Created to prepare soldiers for the nightmarish reality of urban warfare, it is a virtual world locked in eternal civil war. Its thirty million digital inhabitants are ruled by duplicates of some of history's cruellest tyrants: Reinhard Heydrich, the architect of the Holocaust; Beria, Stalin's arch executioner; Torquemada, the pitiless Inquisitor General; Robespierre, the face of the Reign of Terror. But something has gone badly wrong inside the Demi-Monde, and the US President's daughter has become trapped in this terrible world. It falls to eighteen-year-old Ella Thomas to rescue her, yet once Ella has entered the Demi-Monde she finds that everything is not as it seems, that its cyber-walls are struggling to contain the evil within and that the Real World is in more danger than anyone realises.