What is the theme in Soulless by Gail Carriger?

Love conquers all is a theme in the story. When Maccon is able to stop the attack on Alexia when he is a full blooded werewolf proves the strength of love. The reader has been told that he has to be alone in his cell during the full moon because no one is safe. They can't even leave furniture in the cell with him, or he will use it to fight his way out. Love for Alexia overcame his animal instincts to kill. Although his animal side saw her as food, he controlled the instincts to attack her.