The Amber Citadel

Humans share the world with the shape-changing Bhahdradomen, who they defeated in war centuries ago, and the mysterious Aelyr, who keep apart but also consider the Bhahdradomen as enemies. Now, the shapechangers' wiles inflame a king's madness and lead to war and murder. Two sisters and two brothers from a quiet village are about to be dragged into the conflict, where they will find unlooked-for destinies.