Cannibalism isn’t related to the main story or Chris McCandless, it was briefly mentioned in relation to other people who have gone into the wilderness and died/almost died. Tagging suicide, its briefly mentioned that some believe that Chris went out to Alaska with the intention to die there, but this is not true according to the author. Starvation is not a tag, but I would note that as moderate to graphic for the last chapter, which discusses the final month. It’s not gory, but it is detailed.