THE SUN CAME DOWN by Percy Bullchild (Harper & Row: $22.95). "The Sun Came Down," a collection of Native American lore by Blackfoot storyteller Percy Bullchild, recounts the journey of a people from creation through centuries of tradition and change. In this simple yet captivating narrative, 70-year-old Bullchild shares a lifetime of oral history and mythology as told to him by his tribal elders. Vivid tales of mythic beings, monster slayers and Napi, the Coyote "trickster," reveal the ancient teachings and search the landscapes of racial memory for a balance between conflict and harmony. In keeping with the tradition of the storyteller, Bullchild extends the folklore to include his own life experience and perceptions. This unique book possesses rare elements: whimsical adventure, spiritual insight and ancient wisdom. It is a gift from generations past to those who will shape the future and exemplifies the Native American belief that creation is never complete.