Studies in John's Gospel: Stephen Irving

Why is John's Gospel so different to the other accounts of Jesus' life? This book proposes the view that John's approach is thematic rather than biographical, and that once understood, this sets the interpretation of John's gospel into clear context. John himself identifies this chosen themes; he tells us (john 20.31 NKJV) that the things he recorded were written that:
1 - you may believe that Jesus is the Christ, the Son of God, and
2 - that believing you may have life in his name.