What is the author's style in Brave Companions by David McCullough?

Born in Pittsburgh, PA, and educated in English there and at Yale University, David McCullough becomes interested in history and jumps into the demanding discipline as an amateur. Now the much-acclaimed author of biographies (presidents John Adams, Theodore Roosevelt, Harry S. Truman) and chronicles of great human undertakings (the Johnstown, PA, dam, Panama Canal, and Brooklyn Bridge), all intended to allow non-specialists to feel the times about which he writes, McCullough brings together in this volume seventeen portrait sketches, prepared over some twenty years and previously published in journals or delivered as speeches.