From the earliest times, the Gospel of John has been attributed to John the son of Zebedee. John was not only one of the original 12 disciples but, along with his brother James and fellow fishermen Peter, he was a part of Jesus’ inner circle. Since the author makes many self-allusions, there is plenty of internal evidence that supports John as the writer. John can be identified along with Andrew as originally being a disciple of John the Baptist (1:35-42). However, after John the Baptist identifies Jesus, they both become disciples of Jesus. Through the rest of the book John refers to himself cryptically as "the other disciple" or "the disciple whom Jesus loved." This rather than being a statement of arrogance points to John boasting in the love of Jesus as opposed to painting himself as a favourite, although we do learn that John is a faster runner than Peter (20:4).
Likely written around 80-95AD, the Gospel of John was written later than the Synoptics and seems to presuppose their existence. As a result John doesn’t set down all the events he recalls of Jesus’ life but focuses on specific events which he uses to communicate his message.
As a firsthand account John includes specific details not found in the Synoptics. An example of this is supplying the name of the High Priest’s servant (Malchus) whose ear was cut off (18:10). In the Synoptics the 12 disciples are listed but only Peter, James and John play active roles (with Andrew occasionally grouped with them). However, it is in the Gospel of John that Philip, Thomas, Nathaniel and Judas (not Iscariot) all appear.
Most of John’s material is unique and found nowhere else. Some prominent examples are the raising of Lazarus from the dead and washing the disciples feet; not to mention His conversation with Nicodemus, His proclamation as the bread of life and His lengthy discourse and prayer at the last supper.
Unlike the synoptics the book centres on Jerusalem with the Galilean Ministry falling into the background. No parables are given, no exorcisms, and though the Kingdom of God is mentioned, this only occurs 3 times with John using the language of eternal life instead. Teaching occurs throughout but this takes the form of lengthy dialogues and discourses as opposed to the pithy sayings and shorter speeches found in the Synoptics. John choses to focus on the many theological discussions Jesus has in Jerusalem and carefully selects 7 miraculous signs He performed to reveal who Jesus is.
Moreover in the Synoptics Jesus’ identity as God is implicit whereas in John’s Gospel, it is explicit. This is seen in the introduction, in the words of Jesus Himself and the “I am” statements found throughout the book. Jesus is the eternal Word of God who took on flesh and dwelt amongst us. Jesus is identified by John as the lamb of God who takes away the sins of the world (1:29). Using the language of the sacrificial system, Jesus is identified as the means by which God will make atonement for the sins of humanity. The Gospel was written to Christians that they might continue to believe in the person and work of Christ and that through believing they might have eternal life (John 20:30-31).
The exact outline of the Gospel is debated but a loose threefold division can be determined with a subdivision into two parts for the main body.
Prologue 1:1-18
Body 1:19-20:31
-Jesus’ Ministry 1:19-12:50
-Jesus’ Passion 13:1-20:31
Epilogue 21:1-25
The prologue establishes who Jesus is from eternity. The body covers the major work of John’s gospel. This can be further divided into two parts, the first being Jesus’ ministry and the second part covering the events surrounding His death and resurrection. The book ends with an epilogue with a post resurrection appearance whereby Jesus restores Peter and commissions him to look after His flock.