Anyone reading through the first three Gospels—Matthew, Mark, and Luke—will immediately notice their striking similarities. The three tell many of the same stories, sometimes with identical wording, and follow the same basic storyline. Because of these similarities, these three are called the “Synoptic Gospels” (synoptic means “a common perspective”). While ninety percent of Mark’s stories appear in either Matthew or Luke, ninety percent of the Fourth Gospel—the Gospel of John—is unique. One commentator calls John the “maverick” Gospel, an appropriate designation for this unique book.
This section is called the "Book of Glory” because Jesus’ saving work—his death, resurrection, and exaltation—is repeatedly referred to as his “glorification” (John 7:39, 8:54, 11:4, 12:16, 12:23, 13:31, 14:13, 17:1, 17:4–5). It is called this because these events bring glory to God (John 13:31, 14:3, 17:1, 17:4), restore the glory to the Son that he had before the incarnation (John 8:54, 11:4, 12:16, 12:23, 17:1, 17:5), and result in our glorification/salvation.
The Epilogue (ch. 21)
John’s Gospel concludes with an Epilogue, which appears to have been added after the author’s death. Its purpose is to tie up loose ends. It includes another resurrection appearance and a miraculous catch of fish (John 21:1–14), the restoration of Peter after his denial of Jesus (John 21:15–19), and the identification of the author as the “the disciple whom Jesus loved” (John 21:20–25), a character who has appeared repeatedly in the story (John 13:23, 19:26–27, 20:2, 21:2, 21:7).
Though the author is not named, Church tradition identifies this “Beloved Disciple” with John the apostle, the son of Zebedee and brother of James. This makes good sense, since the Gospel associates him with Peter as one of Jesus’ closest disciples (John 13:24, 18:15, 20:2–7, 21:7, 21:20–25). We know from the Synoptics that Peter, James, and John formed a kind of “inner circle” of disciples (Mark 5:37, 9:2, 14:33). Since James died at an early date (Acts 12:2), John remains the most likely candidate.
Church tradition tells us John went to Ephesus where he ministered for a number of years and it was there he wrote his Gospel and the letters that bear his name (1–3 John). As the last of the surviving apostle, he viewed his role as a standing firm for the truth against those who would deny it (see 1 John 1:1–3, 2:18–27). He remained passionate to proclaim the One who was “the way, the truth and the life” (John 14:6).
Mark L. Strauss is a professor of New Testament at Bethel Seminary San Diego and author of numerous works, most relevent to today's topic being "Four Portraits, One Jesus: A Survey of Jesus and the Gospels." We would recommend any serious student of the Gospels give it a thorough read!