The gospel of John is unique among the four gospels. It focuses on Jewish festivals and the last week of the life of Jesus Christ. John 20: 31 shares the purpose of the book: so that we might believe that Jesus is the Christ, the Son of God, and that by believing we might have life in his name.
The first 12 chapters have been called by some the “Book of Signs”. The first sign in Cana is in 2: 1-11 
and the second sign is in 4: 46-54. After the prologue in 1: 1-18 chapters 2-4 deal with Jewish institutions: ritual purification, the temple, a rabbi and a holy well. Chapter 5-10 deal with Jewish festivals: Sabbath (chpt.5), Passover (chpt. 6), Tabernacles (chpts. 7-9) and Dedication (chpt. 10). Chapter 11 reveals the death and resurrection of Lazarus which prefigure the passion of Christ. Chapter 12 begins his last week.
John 13-21 is known by some as the “Book of Glory”. Chapters 13-17 are Jesus’ farewell discourse. The Holy Spirit and hope, trials and revelation are central to chapters 14-16. After his priestly prayer in chapter 17, darkness comes through his arrest, trial (chpt. 18), and death (chpt. 19). The triumph of the light is signaled by the resurrection in chpt. 20 and the epilogue in chpt. 21.