Adventure, Western, Coming-of-Age
All the Pretty Horses involves gunfights, horse riding, ranches, and bare, tumbleweed-tossed towns—so yeah, it's a western all right, even if it is set in the mid-20th century. It's also packed with adventure, as the focus is on action and exploring a strange land. It could be called a coming-of-age novel in the sense that John is a young man and is changed by his romantic experience with Alejandra, but in many ways it seems as if the boys of All the Pretty Horses have already come of age before their time.
John is tough and precocious in ways that seem well beyond his years, and Blevins, though only 13, seems to be a mixture of innocence and deadly experience. Like other westerns, this one ends with the hero wandering into the sun. But rather than attaining adulthood, reaching a goal, or getting the girl as in the sunnier entries in the western and coming-of-age genres, John ends up wandering without a direction, without the one he loves, and without having attained anything other than a perpetual sense of not belonging anywhere. Which places this novel in the most prolific genre of all: bummer books.