John is the forth book of the New Testament and the forth Book of Gospels.
the purpose of the gospel of John as follows: “But these are written that you may believe that Jesus is the Christ, the Son of God, and that believing you may have life in His name” (John 20:31). Unlike the three Synoptic Gospels, John’s purpose is not to present a chronological narrative of the life of Christ but to display His deity. John sought to strengthen the faith of second-generation believers and bring about faith in others, but he also sought to correct a false teaching that was spreading in the first century. John emphasized Jesus Christ as “the Son of God,” fully God and fully man, contrary to a false doctrine that taught the “Christ-spirit” came upon the human Jesus at His baptism and left Him at the crucifixion.
The gospel of John includes only seven miracles—John calls them “signs”—to demonstrate the deity of Christ and illustrate His ministry. Some of these miracles and stories, such as the raising of Lazarus, are found only in John. His is the most theological of the four Gospels, and he often gives the reason behind events mentioned in the other gospels. The gospel of John shares much about the approaching ministry of the Holy Spirit after Jesus’ ascension. There are certain words or phrases that create a recurring theme in the gospel of John: believe, witness, Comforter, life – death, light – darkness, I am, and love.
The gospel of John introduces Jesus Christ, not from His birth, but from “the beginning,” before creation. John calls Jesus “the Word” (Logos) who, as God Himself, was involved in every aspect of creation (John 1:1–3) and who later became flesh (verse 14) in order that He might take away our sins as the spotless Lamb of God (verse 29). The gospel of John includes several spiritual conversations, such as Jesus’ talk with the Samaritan woman that shows Him as the Messiah (John 4:26) and Jesus’ meeting with Nicodemus that explains salvation through by His vicarious death on the cross (John 3:14–16). In the gospel of John, Jesus repeatedly angers the Jewish leaders by correcting them (John 2:13–16); healing on the Sabbath, and claiming traits belonging only to God (John 5:18; 8:56–59; 9:6, 16; 10:33).
The last nine chapters of the gospel of John deal with the final week of Jesus’ life. Jesus prepares His disciples for His coming death and for their ministry after His resurrection and ascension (John 14–17). He then willingly dies on the cross in our place (John 10:15–18), paying our sin debt in full (John 19:30) so that whoever trusts in Him will be saved (John 3:14–16). Jesus then rises from the dead, convincing even the most doubting of His disciples that He is God and Master (John 20:24–29).
(Note: Description used with permission from www.gotquestions.org)