The Bounty Hunters by Elmore Leonard (1954) Houghton Mifflin 

A novel that set standards for other western books.  David Flynn, a former scout sees the Apache as something more than a savage.  There are the rurales, former bandits who are considered the local police, but are out to rob whomever they can.  And there are  the bounty hunters who are paid for scalps of Apaches or Mexicans being passed-off as Indians.  Some of the bounty hunters are just plain murderers who want to kill all native Americans, no matter what tribe.