There are already plenty of books within the Bible (66 to be exact for Protestants), but Matt on The Leftovers thinks there needs to be a modern addition. With the help of John's son Michael, Matt created the Book of Kevin on The Leftovers. Not only was "The Book of Kevin" the name of the Season 3 premiere, but it's also the name of the book that Matt and Michael wrote about Kevin's life. While Kevin was outraged at the existence of this secret text, part of him (the part that attempts to kill himself on the regular to confirm he can't die) knows there is something mystical about himself. So what exactly is the Book of Kevin — and will it somehow prove that Kevin really is a Jesus-like figure?
In the Christian Bible, there are books that make up the Old and New Testament. The New Testament focuses on the existence of Jesus, particularly with the four gospels. These gospels, written by Matthew, Mark, Luke, and John, tell similar stories of Jesus' life, but are not identical. Although Matt didn't say that Kevin was Jesus in the Season 3 premiere of The Leftovers, it's undoubtedly no coincidence that two of the men responsible for the creation of the Book of Kevin are named Matt and John — just like the gospel authors. It was also no coincidence that "The Book of Kevin" aired on Easter — the day that Jesus rose from the dead. That's because the Book of Kevin is acting like a gospel of Jesus, except its subject is Kevin Garvey.
While Kevin has been thinking he is just sharing anecdotes about his life with his partner's brother, Matt has been having Michael write these stories down to compose an exhaustive book about him. That's because they presume Kevin is some sort of savior for the people left on earth after the departure. So stories like Kevin serendipitously meeting Laurie on his birthday turn into stories of fate when interpreted by Matt. And just like the gospels feature Jesus' baptism, Matt noted that the Book of Kevin will also feature Kevin's reluctant baptism.
As much as Kevin doesn't want to admit that there's something special about him, Kevin doth protest too much. And his reluctance to believe in any sort of spirituality is wholly endearing to me. He doesn't know why he keeps surviving things that would kill other people, but he's actively attempting to not search for meaning in it. That's the opposite of what Matt, Michael, and John are doing as they yearn for answers to explain the departure and the chaotic aftermath — and that desire for understanding is how they ended up creating the Book of Kevin. That, plus the crazy and unbelievable life Kevin Garvey does lead.
The Book of Kevin acts as Matt's addendum to the New Testament and most likely paints Justin Theroux's character as a savior or the second coming of Jesus in the days leading up to the end of the world. But as I'm not naive enough to think I understand where The Leftovers will take its story, I'll have to wait and see exactly what the Book of Kevin entails and if there is any meaning to it — and isn't that what the mystery of faith is all about?