Second book in a series where a girl and a boy are trapped on a floating metal city. They are trapped because the girl is a ghost and she's being held hostage. Read around 2016-2018.

[Lucy]

When I read this book I thought it was the first book in the series, so I stopped reading a couple of chapters in but I remember the story vividly.

-The second book starts with two inseparable sisters. I believe one of the girl's names is Nova. They both have special powers and one sister in particular wanted. People in a flying ship come down and take away one sister, leaving the other stranded in their hometown.

-Then the perspective switches. We are now looking through the eyes of a boy. He's in a flying city made completely of metal. His love, a girl, has just died and another girl, presumably the main villain, has resurrected the fallen girl as a ghost. However, the ghost girl cannot run away because she will die again if she leaves the necromancer's magic range. This leaves the two trapped.

-The boy can manipulate metal.

-The boy and the girl have a moment in a room where they both make birds using their powers. The girl manipulates her body (she can change it however she wishes because she's a ghost) to create a bird that can sing but not fly (because if it separates from her main body it will fade). Meanwhile, the boy creates a metal bird that can fly, but not sing. Together they remark that if their birds combined they could make a fully functioning creature.

[Becca]

Muse of Nightmares by Laini Taylor? It's the sequel to Strange the Dreamer.

[Kris]

Google Books preview of Muse of Nightmares (book 2 of Strange the Dreamer series) by Laini Taylor - Becca's suggestion:

- https://books.google.com/books?id=YJB...
- There are different cover images.