Justin Denzel was an American author of children's and young adult books. He was born in Clifton, New Jersey in 1917. As a child he showed an early interest in nature that was to reappear later in his books. He worked for some years in Alaska, where he wrote for an Alaskan newspaper. He gave up writing after an unsuccessful attempt to write an adult novel, however when he returned to writing he realized he liked to make short stories and children's novels more. Many of his books featured nature and animals and tend to have a historical setting.
I managed recently to win an Amazon gift certificate and decided to blow it on horse books I used to have when I was a kid. I thought I had read this before, but now I think I mistook this for a short story called "Black Kettle Who Once Ruled the Ranges" which can be found in some American horse story anthologies of the great cheap hardback era.
However, I'm still glad I bought this book. It's a lovely compact story of a wild black stallion and the Indian boy, relative of the great Chief Black Kettle, who wants to keep him wild. The illustrations are lovely in a flowing, liquid dappled way. Black Kettle (the horse) is presented as a thoroughbred-type, which is possible since some thoroughbreds turned rogue did survive at least long enough to mate on the range.
When I was done reading this, I admit to hugging the book to my chest. I hope I don't lose this one!