In the final scene of The Leftovers, Nora goes on an Emmy un-nominated monologue about her visit to the other world.
Converse to the present world, there’s a world where 98% of the population disappeared. There’s barely anybody there, and after a bit of a struggle she is able to see the family that she lost, nearly complete and happy. After the departure she could not believe how unlucky she was to have lost her entire family, but now she realizes that in fact her family was lucky that they got to be together. She then tracks down the scientist who built the machine and went over, and she convinced him to send her back.
What a nice story...if only it were true.
What we have instead is a lie Nora tells herself to finally find closure with her terrible loss. As the scientists suspected, she chickened out and wasn’t actually interested in seeing what would happen in the machine. Matt carries her secret to the grave, knowing that he’d never see her again.
A few episodes earlier, Kevin calls Laurie in the midst of a nervous breakdown. Laurie later explains to him that he’s in a delusional state, and you’re not supposed to break a delusional person’s reality. However, she points out that Kevin called her, which is him subconsciously asking for help. She thus treats Kevin using her expertise in psychotherapy.
Who does Nora call from a payphone? Who has Nora been talking to every month for the past few years? Why it’s psychoanalyst Laurie! Laurie uses the same techniques she used with Kevin - gently leading Nora out of her own delusion without breaking the reality. She’s letting Nora believe that the 2% who disappeared are all in a mirror world and her family is happy.
Ok so what did happen to the 2%? We’ll never know. And that’s exactly the point. In a sense, as people pass, we are constantly leftovers. And we find stories to help us cope. But what happens when every single story falls short because of a cataclysmic, once-in-a-lifetime event? We have to make new ones to stave off the madness: thus the book of Kevin.
And what is the Book of Kevin? It’s a gospel. And like the gospels, it’s being read hundreds of years from when it actually happened, with some truth, a lot of exaggeration, and millions of fervent believers.