Law of the Wolf Tower by Tanith Lee
Published by Hodder

Claidi has lived all her life in the House, protected by guards from the dangers of the Waste. She is now a servant to the spiteful Princess Jade Leaf. Then one day a balloonist is shot down by the guards - a glorious golden haired young man called Nemian whom she is easily persuaded to rescue. They flee across the Waste, encountering both friends and enemies - and it is not always immediately clear which is which. For Claidi the greatest challenge comes after their arrival at the Wolf Tower, Nemian’s home, where she needs to draw on all her strength and wits to secure her future.