This story centers on a young princess, who is married off to the aged king of a rival kingdom. They both enter the marriage with expectations that neither can fulfill. I liked the story and have another book by this author that I want to read, but Horses of Heaven had several shortcomings.
The author handled the narrative awkwardly. The story is told by one of the queen's attendants many years after the events of the story took place. The narrative switches from 1st person to 3rd person, from present to future.
There is a bit of fantasy in this novel, but it is not a main part of the book -- until the end. For a book that I felt was very enjoyable and interesting, the ending was ridiculous in large part to the fantasy element that was thrown in. It was wrapped up too quickly and with too much contrivance so that it could fit under the heading of "And they lived happily ever after."