Terciel & Elinor by Garth Nix (Book 1 - The Old Kingdom)

In the Old Kingdon, a land of often terrible magics, eighteen-year-old orphan Terciel studies necromancy - but not to raise the dead, rather to lay them to rest. He is the Abhorsen-in-Waiting, whose task it will be to make sure the dead do not return to life.

Across the Wall in Ancelstierre, where magic does not usually work, Elinor, nineteen, lives a secluded life, her only friends an old governess and an even older former circus performer. Her mother is a tyrant, feared by all despite her impending death…  

Elinor does not know she is deeply connected to the Old Kingdom, until a plot by an ancient enemy of the Abhorsens brings Terciel to Ancelstierre. In a single day of fire, death and loss, Elinor finds herself on a path that will take her into the Old Kingdom, into Terciels life, and will embroil her in the struggle of the Abhorsens against the Dead who will not stay dead.