Slaves, Tolkien, Tuchman, art; Unfinished Tales, by J. R. R. Tolkien. Boston: Houghton Mifflin Company. 472. pp. $8.25.

Christopher Tolkien has carefully organized his father's raw and unfinished drafts, supplying abundant explanation and commentary. He presents the tales chronologically, in the context of the development of Middle-Earth. But, Middle-Earth assumes an intricate history spanning three ages with numerous novel creatures and possibilities. Consequently, the younger Tolkien describes the tales with the familiar terminology of ''hobbits'' and ''orcs.''

The stories may bring some confusion to readers because they contradict earlier works. But to a Tolkien fan this book will likely provoke more fascination than frustration.