Fiction for Young Readers : THE LEGEND OF JIMMY SPOON <i> By Kristiana Gregory (Gulliver Books/Harcourt Brace Jovanovich: $15.95; 159 pp.; ages 8-12)</i>

Here’s a puzzle: Would a 12-year-old white boy, taken from his home and family--unexpectedly but not altogether unwillingly--and plunked into a place of honor with an Indian band, accept his new role without question or objection?

The year is 1854, the place Utah. Jimmy Spoon is mad at his father because he can’t have a horse until his 14th birthday. Two Indian boys appear and offer him a horse if he’ll visit their chief’s mother--or that’s how Jimmy understands the invitation. Once he reaches the Shoshone camp, it becomes clear that the Indians mean for him to stay and be Chief Washakie’s little brother. Why? Jimmy doesn’t ask. He finds out much later, and then only by accident.

He spends three years with the Shoshone, learning their ways and becoming a respected tribe member in his own right. Then he goes back to his family. That’s it. That’s the whole tale.

This is a piece of historical fiction rich in its portrait of Indian philosophy and daily life but skimpy in the basics of story: character and plot. Jimmy learns to hunt, fish, tan hides and pluck the tail feathers of an eagle without harming the bird. He slowly becomes aware and ashamed of white people’s imperialistic brutality toward the Indians. He observes how the Indian notion of a Great Spirit figures in all aspects of life, in contrast to the once-a-week religion he grew up with. He questions the need for war, and ultimately gets a chance to prevent a war by his own action.

But why don’t the Indians wonder why he so eagerly leaves his family and community? They don’t ask him about it until the very end of the book. Why doesn’t he ask them why they want him in the first place? And there’s the matter of scalping, which is described but unfortunately not explored. Why doesn’t Jimmy ask for some explanation or justification of an act he finds so repulsive? Why doesn’t Jimmy try to contact his parents, and why do they wait three years before trying to get him back?

Compressing three years’ time into a children’s book may leave little space for adequately developing character. Still, there’s not enough depth even to the central figure of Jimmy to make us laugh with him, ache with him, or care very much what happens to him.