Chris McCandless was disillusioned with society. When he found out some of the details surrounding his father's first marriage, he felt disappointed and betrayed. He seemed to believe he did not need money, relationships or comfortable housing in order to be happy. He seemed to feel that going into the wild would free him.
The author, Jon Krakauer, seems to see Chris as an adventurer. He dismisses the common viewpoint that Chris did not understand his surroundings or the risks associated with living in the Alaskan wilderness.
Others might see Chris as a person with a mental illness who was unable to deal with reality.