While the diary is a significant part of the story told in Jon Krakauer's book "Into the Wild," the diary itself is in the possession of McCandless's family.
It's been reported that the family is protective of the diary, and it's not available for public viewing or publication. They likely feel it's a personal and private document that should not be shared widely.
However, excerpts from the diary were used in Krakauer's book, and they provide a valuable insight into McCandless's thoughts and experiences.