The Plains Indian Sign Language, PISL. Is a endangered language loosing out to ASL. This book shows many of the signs, and while I can't verify how accurate they are protrayed and if you'll learn to use correctly, I feel sign language of any nature is better learn visually than through a picture book. It does show how different these signs are from ASL, and sadly like many Native American Tribe verbal languages what we are loosing in culture and history.
My daughter was very good about teaching her sons ASL along with teaching them their words, so even before they spoke, they could use and read hand signs. I am passing this along to her that she could teach her boys these as well. We live in Oklahoma, the home of many the Plains Indians who use this language.