The Prince of the Icemark by Stuart Hill
When his brother, the King, is killed in battle, Prince Redrought must rally his people and learn to defend the tiny country against supernatural invaders - werewolves, vampires and zombies. Redrought must take the fight to enemy territory, The-Land-of-the-Ghosts, and it's there he will fall or stand for ever in the legends of the Icemark as King Redrought Athelstan Strong-in-the-Arm Lindenshield, Bear of the North.