Horse & Pony Books:
(SCHOLASTIC [USA] 1998)
Reprinted in paperback by Scholastic.
SUMMARY: Historical horse story set amongst the Native American Indian peoples in the 1700s. There is nothing young Running Crane wants more than to have a horse of his own, and he dreams of riding not just any horse, but the spirit horse of the Snake People - a majestic and wild white stallion. But Running Crane isn't a very good rider, and is bullied by the other more proficient boys. When he joins the warriors in a horse raid on the Snake People and is separated from the rest of his party, he discovers the beautiful spirit horse alone on the prairie. At last, he has the chance to prove his worth and make his dream of taming a magnificent horse come true.
Very easy to find in the USA. At the moment it can also be ordered from Amazon UK, although in general it is harder to find in the UK than in America.