How do chapters 14 and 15 explain Krakauer’s purpose for writing this novel?

I think these chapters illustrate Krakauer feeling a personal connection with Chris. It is only in these sections that Krakauer truly becomes a character in Into the Wild, more than just narrator, investigator and interviewer. In his story of climbing the Devils Thumb, he illuminates a lot of parallels between himself and McCandless, and we see how he probably can understand McCandless’s motivations deeply, without having ever met him, because of their similarities in life circumstances and personalities. This does raise the question, however, of if he can really tell this story impartially, or might he be imposing his own story onto McCandless’s, which, with his death, can never be completely known.