But that part of us greater than the sum of our parts cannot begin and cannot end, and so it cannot fail.
So I know she forgives me, just as I forgive her. Thomas Edison's last words were: "It's very beautiful over there." I don't know where there is, but I believe it's somewhere, and I hope it's beautiful. (136after.17-18)
Miles's ending is both climactic and anti-climactic. It occurs in the middle of the bustle of the end of term, when two of the major players have already left. Miles gets Takumi's letter admitting his own responsibility in Alaska's death, and Miles can't even get closure from him because he already left for Japan. The only person left on campus is the Colonel, but he's conspicuously absent from the last scene. Miles must, like everyone else, navigate his grief alone.
And he does. For a book riddled with dialogue, it's notably absent in this last chapter. So Miles writes his way "out of the labyrinth" (136after.11) in the form of his final essay for the Old Man. The letter is a way for Miles to record his own last words about Alaska's death and a way for him to grasp that closure that eludes him.
Of course he can't avoid getting one last set of famous last words in there: "Thomas Edison's last words were: 'It's very beautiful over there'" (136after.18). We can take this to mean that beauty means more than physical beauty, that it means the suffering Alaska experienced in life hasn't followed to wherever she is now. And although Miles never figures out whether Alaska's death was accidental or intentional, he is able to forgive himself and forgive her. Things look a lot brighter for Miles and Alaska after a tortuous journey through death and grief.