Even when Peter Matthiessen writes the text in a book full of photographs (''The Tree Where Man Was Born,'' with Eliot Porter's pictures of Africa) he goes for literature as well as information. This is both a strength and possible drawback in the 600 gray, unillustrated pages of ''In the Spirit of Crazy Horse.''
Matthiessen's literary art pulls you along. There is the resonance with history, as he recalls the 19th-century massacre of Indians at Wounded Knee while describing the past decade's often violent events in the same Pine Ridge reservation area of South Dakota. There is the skilled interweaving of past and present individual voices to tell a story of treachery, corruption, and courage on and off the reservation, in and out of government. There is the distinctive presence of the author's own voice, letting admiration, indignation, and sarcasm glint through. The result: an eloquent recital of wrongs done to the Lakota people, along with latter-day efforts to right them, justice gone astray, and lands plundered for newly found mineral resources in defiance of bygone treaty obligations.
The possible drawback is that the very elements making for distinction may undercut the persuasiveness of the case Matthiessen offers. When he adds more and more to his rich investigative mixture, the clear thread of argument becomes slack. When he lets his mockery of government officials, however justified, edge his prose, there is the danger of indictment being taken for polemic, of assent from the already convinced turning to doubt from readers on the fence.
The likelihood is that unadorned facts would carry the day anyway. Just as prosecutors' use of false evidence against Indian defendants has brought judicial reprimand as well as Matthiessen outrage.
Leonard Peltier is the principal defendant to whom the author believes justice has still not been done, the only one of four indicted members of the American Indian Movement (AIM) to be convicted of murder after two Federal Bureau of Investigation agents and one Indian were killed in the Oglala shootout of 1975. The record traced by Matthiessen suggests ample reason for a judicial review of the case.
Did the FBI have reason to react to AIM Indians as terrorists? Here is the testimony of then FBI director Clarence Kelley, the first FBI director to serve as witness in a court trial: ''It is my very definite knowledge that the American Indian Movement is a movement which has fine goals, has many fine people, and has as its general consideration of what needs to be done, something that is worthwhile, and it is not tabbed by us as an un-American, subversive, or otherwise objectionable organization.''
Matthiessen cites an honest, intelligent federal Bureau of Indian Affairs agent when he finds one and notes better and worse administration policies. He quotes a Lakota elder who speaks of ''comparative happiness'' on the reservation in the early days, despite children being sent away to school and religious ceremonies interfered with; there was farming and food storage not available before.
But then came the usurpation of reservation lands, the training of Indians in dependency, the manipulation of tribal councils, the on-again off-again efforts to ''terminate'' the tribes and force Indians into assimilation.
Matthiessen fleshes out the story with documents obtained through the Freedom of Information Act. It is shot through with tragedy but with Indian humor and bizarre detail, too. You're reading along, and there is a comedienne you recall with delight from an old Broadway musical: She is said to have become an FBI informer infiltrating AIM.
For all the exploration of recent controversy, perhaps the prime contribution of ''In the Spirit of Crazy Horse'' for the reader is its immersion in Lakota life and lore. Here is an author who does not overlook anybody's human failings but who conveys with respect a sense of the achievements, setbacks, and spiritual yearnings of people in conditions ''almost unimaginable to most Americans.''