Sewell's intention in writing the book was to promote the humane treatment of horses. Called the "Uncle Tom's Cabin of the Horse," Black Beauty is credited with having the greatest effect on the treatment of animals of any publication in history. The book resulted in legislation protecting horses and a changed public attitude about animal pain and the traditional and fashionable practices that caused suffering for horses.

Black Beauty was the only book that Sewell wrote, and she sold the manuscript for only twenty pounds. It is still one of the most widely read books in the world, with numerous translations and multiple media versions. Barely a year goes by without a new print edition being published, thus continuing the life of this timeless classic.