It was originally a book by Jon Krakauer, he was able to trace McCandlesses wanderings thru the western US during the 2 years before his death. He had stopped communicating with his family, but they hadn't filed a missing person's report. It's on many high school/college reading lists, it really speaks to the craving many young people have to be free, and is quite poignant if you can empathize with him (some people just criticize him as naive). Fabulous film version, as well.
ETA I can't help but assume someone is going to write this man's story, as well, since the book Wild, about hiking the Pacific Crest Trail, was also a huge success.