Arm of the Sphinx (Books of Babel Series #2) by Josiah Bancroft

Senlin continues his ascent up the tower in the word-of-mouth phenomenon fantasy series about one man's dangerous journey through a labyrinthine world.

"One of my favorite books of all time" — Mark Lawrence on Senlin Ascends
The Tower of Babel is proving to be as difficult to reenter as it was to break out of. Forced into a life of piracy, Senlin and his eclectic crew are struggling to survive aboard their stolen airship as the hunt to rescue Senlin's lost wife continues.

Hopeless and desolate, they turn to a legend of the Tower, the mysterious Sphinx. But help from the Sphinx never comes cheaply, and as Senlin knows, debts aren't always what they seem in the Tower of Babel.

Time is running out, and now Senlin must choose between his friends, his freedom, and his wife.

Does anyone truly escape the Tower?