Showing The Nex by Tim Pratt

Teenager Miranda Candle finds a mysterious necklace and is suddenly transported to The Nex, the bizarre city at the center of all possible universes, where she falls in with a pair of would-be revolutionaries - the skinshifter Howlaa and the bodiless Wisp - fighting the oppressive regime of the city-state's Regent and his army of steam colossi, cynical cyborgs, and the depraved royal orphans.