John is one of Christ’s disciples who followed Him along the dusty trails of Judea, Samaria and Galilee. Many doubted that John wrote this book whose plainly-stated theme is that Jesus is God.
The discovery in Egypt of the Rylands Papyrus 52 contained portions of John's 18th chapter, dated circa A.D. 135. Scholars peg John as written by A.D. 90.
John's other books (I, II and III John and Revelation) were written after his gospel. Before A.D. 70 Matthew sees Jesus as King; Mark has Him as Servant; Luke as the Son of Man; John has Jesus as God.