Chris McCandless remains an elusive figure even within this biography of his life. Although Krakauer frequently includes excerpts from Chris's personal journals, readers often feel a sense of detachment, partly because Chris wrote about himself in the third person under an alias. Only in his final journal entries does he write in the first person and sign with his real name, perhaps highlighting his dawning realization of his impending death. The tone of these last entries evolves from fear to regret and courage, and ultimately to a sense of peace and acceptance. Apart from these journal snippets, all information about McCandless is pieced together from the accounts of those who encountered him during his travels. These narratives depict him as a highly intelligent and fiercely independent young man, committed to the stern and ancient ideals he absorbed from his readings.

According to recollections from his family and university friends, McCandless appeared to be a well-adjusted twenty-two-year-old at the time of his disappearance. He was athletic, intelligent, and a natural entrepreneur, excelling in various pursuits to the point of overconfidence. A double major with above-average grades, he enjoyed a relatively comfortable and fortunate life. He contributed to the student newspaper at Emory University and, like many of his peers, contemplated the injustices in the world. However, he seemed to take life more seriously than most, opting not to join a fraternity and declaring that, based on his principles, he would neither give nor accept gifts. By all accounts, he was an affable yet intense friend, but there were troubling hints of his discontent with his parents. While he appeared content with his home life, he confided in a few trusted individuals his deep resentment and bitterness toward his parents, whom he viewed as unjustly authoritarian.

Krakauer takes care not to burden Into the Wild with excessive authorial judgment. Although he acknowledges from the beginning that his own feelings about McCandless will become apparent, he makes a concerted effort not to impose his own deeply-held beliefs on his readers. A notable subtext in this biography is how McCandless's story and various other themes seem to illuminate each other for the author. In the introduction to Into the Wild, Krakauer states, "in trying to understand McCandless, I inevitably came to reflect on other, larger subjects as well: the grip Wilderness has on the American imagination, the allure high-risk activities hold for young men of a certain mind, the complicated, highly charged bond that exists between fathers and sons."

A significant theme is the profound and hidden alienation McCandless felt toward his parents. He harbored intense anger toward them, even though his grievances were often unclear. Bitterness and frustration frequently create barriers between strong-willed sons and equally stubborn fathers. Krakauer's depiction of the elder McCandless as a self-made man with a dominant personality makes this a plausible scenario. However, McCandless’s enduring positivism might have enabled him to overcome such an obstacle. Walt McCandless recalls that, despite everything, he cherished spending time with his son. Krakauer suggests that one possible reason for Chris’s enduring animosity could be his discovery of the messy and tension-filled end of his father's first marriage and the beginning of his second. These long-past marital issues seemed to have enraged Chris's strict and unforgiving moral sense, leading him to judge and condemn his father permanently, applying moral standards so severe he did not even impose them on his friends.

Throughout his life, he seemed driven by an insatiable desire to uncover some redeeming truth about humanity through himself. Nevertheless, his insistence on doing things his way led him to overlook several basic precautions that might have kept an experienced woodsman alive: a good hunting rifle with sufficient ammunition, reliable information about the area he was entering, and a dependable U.S. Geological Survey topographic map. Krakauer concluded that the actual cause of Chris's death by starvation was a form of poisoning from eating wild seeds that even experts did not know were highly toxic. Ironically, this was a mistake anyone could have made. McCandless would not have needed to eat the seeds if he had not been trapped by runoff from the Teklanika River, had he possessed an adequate hunting gun, or had a map to show him a crossing point just half a mile from his camp. As one friend later observed, McCandless, given his passion and intensity, sometimes struggled to see the forest for the trees.

Although he remains a mysterious figure, others in Into the Wild are portrayed with more clarity. These include the diverse array of ordinary and extraordinary individuals who briefly crossed paths with and befriended him. Among them are "rubber tramps" Jan Burres and her boyfriend Bob, who encountered McCandless along the United States Highway 101. Jan felt a maternal instinct towards Chris, and he reciprocated with a nearly childlike affection. At other times, Wayne Westerberg provided him with work and lodging in Carthage, a small, industrious town in South Dakota. Another friend, Ronald Franz, had lost his own family in a tragic car accident long before McCandless was born. Franz was deeply moved by Chris's genuine good nature and even asked the young man if he would allow Franz to adopt him as his grandson. McCandless responded with his usual evasiveness; having distanced himself from his own family, it seems he was both drawn to and repelled by parental figures.