What is the author's style in Lame Deer, Seeker of Visions by Richard Erdoes?

Lame Deer, Seeker of Visions, is the story of the American Indian, specifically the Sioux, from a wholly Indian perspective. It is the compilation of all of Lame Deer's memories, his life, the prejudice against and desecration of the native American and his rich heritage, a complete depiction of traditional Indian spiritual beliefs and accompanying ceremonies, legends and rituals, and a condemnation of the white man's mutation and destruction of nature, as well as his ignorance of the dignity of traditional Indian culture. From this perspective, the reader is given a complete picture of the Indian as he was—free to hunt, roam, share, love, and revere his world to the transformation of his life, as the white man moved westward, bringing with him diseases, greed, money, crime, alcohol, and taking the land, by brute force when he desired, condemning the Indian to a life of squalor, alcoholism, poverty, and poor education. Lame Deer makes no excuses for what has been done to his population - all that has happened has been wrought by the white man, and it is clearly and completely unjust, immoral, and, to him, illegal. His premise remains solid throughout. The white man must make changes now. He must cease to destroy the earth; he must return what he has taken from the Indian; he must make reparations for his theft; he must dignify the rich heritage of the Indian by allowing him the rights to practice his traditions and the land on which to do so.