Pen's life is all about secrets: the secret of the city's spirits, deities and monsters her best friend Beth discovered, living just beyond the notice of modern Londoners; the secret of how she got the intricate scars that disfigure her so cruelly - and the most closely guarded secret of all: Parva, her mirror-sister, forged from her reflections in a school bathroom mirror. Pen's reflected twin is the only girl who really understands her. Then Parva is abducted and Pen makes a terrible bargain for the means to track her down. In London-Under-Glass, looks are currency, and Pen's scars make her a rare and valuable commodity. But some in the reflected city will do anything to keep Pen from the secret of what happened to the sister who shared her face. The Glass Republic is the gripping sequel to The City's Son, and the second book of The Skyscraper Throne trilogy.