Author John Krakauer develops characters in this non-fiction book in the same manner that most authors routinely develop characters. Krakauer uses both direct and indirect characterization to build and develop the characters (who are real people) in this book. Direct characterization occurs when an author or narrator directly tells the reader specifics about a character. Indirect characterization occurs when the narrator has the reader deduce characteristics of a character by observing his/her behavior, speech, appearance, and manner of communication with other characters. Additionally, indirect characterization occurs through how other characters respond to a character. What I find great about Krakauer's characterization in this book is how quickly and seamlessly the narration flips and flops between the two types of characterization. Take the following passage for an example.

In many ways, Rob Hall's Adventure Consultants site served as a sort of town hall for Base Camp, largely because nobody on the mountain was more respected than Hall, who was on Everest for his eighth time. Whenever there was a problem—a labor dispute with the Sherpas, a medical emergency, a critical decision about climbing strategy—people came to him for advice. And Hall, always generous, offered his accumulated wisdom freely to the very rivals who were competing with him for clients, most notably Scott Fischer.

In this paragraph, readers are directly told that Rob Hall is both respected and generous. Those details are woven together with great indirect characterization. Krakauer tells us that Hall is respected, but we deduce how much he is respected by seeing that "whenever there was a problem," Hall is the guy that everybody goes to. It's one thing for Krakauer to say that a character is respected, but it's an entirely different thing for Krakauer to show readers this through the behavior of other characters. We also are left to deduce that Hall is quite an experienced Everest climber, since he is on the mountain for the eighth time.