Mustang: Wild Spirit of the West by Marguerite Henry is about the plight of America's wild horses. It led me to become an activist at around age 9 and I continue to pursue issues around Mustangs. I adopted a Mustang from the BLM about 15 years ago and she is a great little saddle horse. When I was a kid I used to write the author all the time and she always answered me; I still have her letters. I loved her other books as well, but this is the one that really stuck with me, although reading Brighty of the Grand Canyon to my kids led us to adopt a miniature donkey named, "The Reckless Peanut."