Crown of Ice

Snow Queen Thyra Winther is immortal, but if she can't reassemble a shattered enchanted mirror by her eighteenth birthday she's doomed to spend eternity as a wraith.

Armed with magic granted by a ruthless wizard, Thyra schemes to survive with her mind and body intact. Unencumbered by kindness, she kidnaps local boy Kai Thorsen, whose mathematical skills rival her own. Two logical minds, Thyra calculates, are better than one. With time rapidly melting away she needs all the help she can steal...