''THE NUTCRACKER ''IS A Christmas tradition, and for most children it is their introduction to ballet. Here, in one beautifully illustrated book, is the story of the ballet and a 78-minute CD of Tchaikovsky's music performed by the Utah Symphony Orchestra. Stephanie Spinner has written a brief, lyrical text about the little girl, Maria, and her Christmas gift of a wooden nutcracker doll who is transformed into a young prince. Together they fly to the Land of Sweets where the Sugar Plum Fairy entertains them with lively and exotic dances from around the world. Peter Malone's exquisite illustrations capture all the magic of the beloved Christmastime ballet.