Revenge

When Eugenides, the Thief of Eddis, stole Hamiathes's Gift, the Queen of Attolia lost more than a mythical relic. She lost face. Everyone knew that Eugenides had outwitted and escaped her. To restore her reputation and reassert her power, the Queen of Attolia will go to any length and accept any help that is offered... she will risk her country to execute the perfect revenge.

...but

Eugenides can steal anything. And he taunts the Queen of Attolia, moving through her strongholds seemingly at will. So Attolia waits, secure in the knowledge that the Thief will slip, that he will haunt her palace one too many times.

…at what price?

When Eugenides finds his small mountain country at war with Attolia, he must steal a man, he must steal a queen, he must steal peace. But his greatest triumph—and his greatest loss—comes in capturing something that the Queen of Attolia thought she had sacrificed long ago...

Books for the Teen Age 2001 (NYPL) and Bulletin Blue Ribbon Best of 2000 Award.