I already knew the basics of the story of Ishi, but this book really opened me up to a lot of different things.
For one, I was shocked at how many tribes were obliterated in California during Westerners' short time there. It actually turned my stomach at a couple points.
For another, I found it kind of appalling that Ishi was living in the museum almost as a living exhibit. It very much showed the racism and the noble savage attitude toward non-Westerners at the time, but I also see that in some ways things really haven't changed with regard to ethnicity.
Finally, I did find it interesting that Sapir, one of the big names in linguistic anthropology, actually did a lot of the recording of the Yahi language by interviewing Ishi. It definitely showed some of the cultural relativism that is practiced by anthropologists today.
What really gets me is that this kind of history is not taught in schools. The way we treated (and continue to treat) Native Americans and other minorities in the United States is utterly appalling, and the only way to show that it's wrong is to teach it in a history class where racism and ethnocide can be discussed in relative detail.