The #1 bestselling chapter book series of all time celebrates 25 years with new covers and a new, easy-to-use numbering system! The magic tree house has returned and it's taking Jack and Annie back in time to Alaska, 1925. There they meet Balto, a jet-black Siberian husky destined to save victims of the diphtheria epidemic. Illustrations. 5 1/4 x 7 5/8.