Nothing (at least that can be done by humans) immortalizes anyone. The Fault in Our Stars will hopefully have a long and wonderful life, but it will eventually go out of print, and eventually the last person ever to read it will die, and then the characters will no longer live in any consciousness.Also, that is okay. That is good, actually. That is how it should be. One of the things the characters in this novel have to grapple with is the reality of temporaryness. What Gus in particular must reconcile himself to is that being temporary does not mean being unimportant or meaningless.