This book combines the frontier adventures associated with living by your wits, your knife, and your six-shooter, with deep insights into the Indian character. I think it is an important book even today, because we look back with shame on the subjugation of the Indians, and we also frequently identify American Indians with the current back-to-nature/environmental movements.
I remember as a kid reading books about the Apaches and wanting them to "win." It's natural, I suppose, to want to freely roam the West, living off the land. But this book dispels that myth. Mr. Cremony shares that the Apaches did not even farm; they lived off of hunting and what they could steal from their neighbors (Comanches, Navajos, Americans, or poor peasant Mexicans - it didn't matter). In fact, that was the surest way to the top of Apache society: the bolder and more brazen a thief you were, the more respected you were and the more wives you could support. The point is that the Apache way of life was completely incompatible with modern society, and a "win" for the Apaches would mean the defeat of virtually everything we think is important today.
So the Apaches had to be subjugated, and the faster the better, for both them and civilization. We look back with horror today on the cruel violence practiced by both sides, but I think the thing to remember is that this was truly a fight to the death. From reading the book, I'm convinced that the Apaches, at least the adults, would never have been able to become productive members of society. From youth they were taught that they were superior to all other races. This belief was in some ways true: Mr. Cremony repeatedly stresses the importance of being constantly on guard when in Apache country, since they would appear out of nowhere to kill you and/or steal everything you owned.
Nevertheless, beliefs such as this meant that the Apaches were like zebras: untamable. There would be no surrender or assimilation into society like immigrants from Europe. They would have to be defeated by force.
Note that Mr. Cremony does not excuse the horrible cruelties committed against the Indians. He is even very critical of how they were managed on the reservations. We can certainly discuss what better methods could have been used, but, in the end, it had to be done.
I also appreciated the book because it illustrated how deep the chasm is between civilized man and the barbarian. I believe this chasm exists regardless of whether we are discussing American Indians or the Germanic tribesmen who fought Rome. It took generations, no, millennia, to civilize Europe. We should have some humility when we judge the actions of past generations, especially if they were moving along the line that has given us the wonders of our modern world.