Seasparrow — Kristin Cashore

Make the harrowing journey home with Queen Bitterblue's sister and spy, in the fifth novel in the bestselling Graceling Realm series.
Hava sails across the sea toward Monsea with her sister, the royal entourage, and the world's only copies of the formulas for the zilfium weapon she saved at the end of Winterkeep. During the crossing, Hava makes an unexpected discovery about one of the ship's crew, but before she can unravel the mystery, storms drive their ship off course, wrecking them in the ice far north of the Royal Continent. The survivors must endure a harrowing trek across the ice to make it back to Monsea. And while Queen Bitterblue grapples with how to carry the responsibility of a weapon that will change the world, Hava has a few more mysteries to solve -- and a decision to make about who she wants to be in the new world Bitterblue will build.