Harris struggled for decades with bipolar disorder, which surfaced shortly after she left high school. Her love of horses became her salvation. She first owned a horse at age 12 when her family "was living the American dream on a cul-de-sac in Santa Rosa," but hard times followed for Harris, along with wild manic episodes. Her illness led to bizarre behavior; at a party she hurled handfuls of chocolate pudding at the walls "as if I were Jackson Pollock (another manic-depressive) throwing paint onto a huge canvas." Buddhism and medications helped, but her personal life was in disarray until she transitioned from homelessness to horse grooming in Ocala, Fla. Working with horses, riding, and training, she got a jockey's license, overcoming the problems of being a woman in a male-dominated sport. "Against all odds," she writes, "at forty years old, I became the first African American woman in Chicago racing history to win a race and only the second in U.S. history." As the book goes into the homestretch, Harris details how she discovered the healing power of horses and got her life back on track. (Mar.)