The Glass Town Game by Catherynne M. Valente

Inside a small Yorkshire parsonage, Charlotte, Branwell, Emily, and Anne Brontë have invented a game called Glass Town, where their toy soldiers fight Napoleon and no one dies. This make-believe land helps the four escape from a harsh reality But on this Beastliest Day, the day Anne and Branwell walk their sisters to the train station, something incredible happens: the train whisks them all away to a real Glass Town.

This is their Glass Town, exactly like they envisioned it…almost. They certainly never gave Napoleon a fire-breathing porcelain rooster instead of a horse. And their soldiers can die; wars are fought over the potion that raises the dead, a potion Anne would very much like to bring back to England. But when Anne and Branwell are kidnapped, Charlotte and Emily must find a way to save their siblings. Can two English girls stand against Napoleon’s armies, especially now that he has a new weapon from the real world? And if he escapes Glass Town, will England ever be safe again?