The Forbidden Book by Sacha Lamb

On the night before her wedding, 17-year-old Sorel leaps from a window and runs away from her life. To keep from being discovered, she takes on the male identity of Isser Jacobs — but it soon becomes clear that there is a real Isser Jacobs, and people want him dead. Her mistaken identity takes Sorel into the dark underworld of her small city in the Pale of Settlement, where smugglers, forgers, and wicked angels fight for control of the Jewish community. In order to make it out, Sorel must discover who Isser Jacobs really is — and who she wants to be.