This is a cute book for what I perceive as the 4th to 6th grade set (8-12 year-olds) about prejudice. Dexter is constantly described as a "half-breed" because his mother is a Thoroughbred and his father is an Arabian ... and told that he will never be a racehorse.
Of course, there's a trainer who sees a little something extra in him and at the end of the day Dexter proves his detractors wrong. Anyone who can't see that coming from the title is not paying attention.
What cost the book a star was some of the factual inaccuracies. A kid who picks up this book is likely to like horses ... and know that horses do not travel or go out into the field in bridles -- that's what halters are for. And Anglo-Arabs (that's what happens when you have a Thoroughbred/Arabian cross) are the third oldest breed in the world. They're considered their own breed because Thoroughbreds and Arabians come from the same genetic pool: the three Thoroughbred foundation sires were all Arabians.
Are these the nitpicks of a former equestrian athlete? Most assuredly. The story is a good one about treating people equally and recognizing that even those who are different are valuable. I just had trouble getting past the things that bugged me.