I remember reading Into The Wild in my twenties and feeling a strong connection to Alex. Even if going to the bus wasn't a wise decision, I feel it's only human to want to cultivate those types of connections. I never went to the bus, but I was definitely curious what Alex was experiencing in the final days of his life.
I agree with GP that it's a cautionary tale, but it's more than that. It's caused thousands of people to think more about the way they live their lives. Seems a bit more substantive than simply trying to get a selfie, don't you think?