Sabriel (adult) (The Abhorsen Trilogy)

For many years Sabriel has lived outside the walls of the Old Kingdom, away from the random power of Free Magic, and away from the Dead who won't stay dead. But now her father, the Mage Abhorsen, is missing, and to find him Sabriel must cross back into that treacherous world - and face the power of her own extraordinary destiny.