Krakauer does in fact base much of his narrative on his own experiences both in the wilderness, and in a somewhat unsettled home life.  In chapeters 13 and 14 Krakauer makes a strong arguement for the ways in which his personal life paralell that of McCandless; the troubles with his father, the desire to challenge nature, stubborness, and a lack of understanding of his own mortality.  Further, Krakauer draws deeply on research of similar adventurous souls who have faced nature and lost.  Krakauer is no stranger to facing death and writing about it.  His critically acclaimed Into Thin Air chronicals the famous Mt Everest expedition, which he was part of, that claimed the lives of numerous fellow mountaineers.

When completing a biography, an author must draw upon what information is available.  Krakauer did extensive research into McCandless - reading the man's journals, looking at school records, interviewing friends and family.  However, because much of the journey is a mystery, Krakauer brings in his own knowledge of the outdoors and of such types of journey's to make educated guesses about what McCandless must  have experienced.  By interweaving his own experience with what he has learned of his subject, Krakauer creates a logical and believable account of McCandless.  His research and his own experience make Krakauer a very reliable narrator.