The Up-and-Under, book 4: Under the Smokestrewn Sky
A. Deborah Baker2023

Since stumbling from their world into the Up-and-Under, Avery and Zib have walked the improbable road across forests, seas, and skies, finding friends in the unlikeliest of places and enemies great in number, as they make their way toward the Impossible City in the hope of finding their way home.

But the final part of their journey is filled with danger and demise. Not everyone will make it through unscathed. Not everyone will make it through alive.