When it comes to the middle book, or in this case the third book, of a series, it gets way more complex. The author Marissa Meyer purposefully separated some characters from others to make a conflict. And that's what makes the story fun, which I love.
Cinder, Carswell Thorne, Scarlet and wolf continues to make an effort of stopping Levana, the lunar queen, from ruling earth. And in this book, they encounter another main character called Cress. Now, Cress is a bit different from the others, she had been locked in a satellite in space for years. Because the heroes all have different personalities, the big problem is actually for them to work together, and be a team.
It is unimaginable how the author managed to create a series of fiction books that completely makes sense. Every time I read something like this is like "wow!" Again, I totally suggest you to read this novel, along with other ones in this series. I can not wait to read Winter and Fairest, the two final books in "The Lunar Chronicles".