"Into the Land of Unicorns" by Bruce Coville

A wonderful fantasy full of adventure, friendship, and courage. Cara jumps into the world of Luster when her grandmother gives her an amulet and tells her to deliver a message, "Find the old one. Tell her... 'The Wanderer is weary.'" This would be easier if there wasn't a mysterious man tracking Cara not to mention the delvers. How will Cara find the old one and deliver her grandmother's message before the tracker or delvers catch her?