The Mustang Herder by Max Brand (Good, 1994, HC, 327 pgs, Thorndike Press Large Print)

Former library book: cover and pages have light wear. ISBN 1560547057

Perfecting his skills in street fighting and gunslinging, New York-born Gregg heads west in the hopes of making his fortune and is disgusted by his subsequent job as a mustang herder, until a band of thugs offers him the adventure he craves.