What is the author's style in Black Elk Speaks by John Neihardt?

Visions of spirits and the spirit world are a recurring theme in Black Elk Speaks. Black Elk experiences several visions throughout his life, but the first—at the age of nine—is the most significant. He believes that this vision contains the key to helping save his people from the Wasichus. In that sense, his vision represents his desire to provide a better life and future for his fellow Sioux. Ultimately, Black Elk considers himself a failure for not being able to use his vision to help his people.