What is the author's style in Beyond the Hundredth Meridian: John Wesley Powell and the Second Opening of the West by Wallace Stegner?

Wallace Stegner writes about John Wesley Powell, but chose to focus on the career and work of the man rather than concentrate on the man's personality. Instead of the traditional biography that begins with the subject's birth and includes all significant events of life such as childhood, ancestry, marriage, and children, Stegner highlights only those particulars of Powell's life that have bearing on his legacy of government service.