From John's gospel we learn that Jesus Christ frees us from the bondage of self, sin and Satan. 

From John 8, we learn how Jesus stoops down to offer mercy to those who least deserve it.   

From John 6 we learn about the dangers of false discipleship, and the difference between those who follow Christ for their own self-interest, and those who have found essential life-change through Jesus Christ.

From chapter 6 of John's gospel we learn three essential truths about Christianity: 1) Jesus is the main subject of the Bible, 2) Eternal life is found in Christ alone, and 3) Christians are those who feed on the crucified One.