I have found that many people treat John's Gospel as the "weirdo" or the "Stepchild" Gospel, left out because it does not fit in with the framework or the elements of the other three Gospels.
In none other gospel does the Holy Spirit inspire the writer to manifest Jesus Christ as fully God!
The other three Gospels do not diminish or dismiss the deity of God becoming man, and Paul in His epistles hammers this truth over and over.
Yet for many believers, they do not have a "John" or "God is Grace" revelation of God.
They have a "Matthew" revelation, in which they see Jesus as a king unapproachable, one whom we must earn the right to visit with. I do not write that Matthew had so limited a revelation, but we must see Jesus in all the scriptures! "Fools and slow of heart to believe" is the heaviest indictment against the church today, I believe, in large part because we are not seeing Jesus Christ in His fulness.
Some of us have a "Mark" revelation, in which we see Jesus as our servant, one who does things for us and provides miracles for us. Now, without a doubt Jesus has come to serve us, giving us all things with Himself, but to see Him only as servant is too miss out on so much more! To use Jesus as a means to an end is just a sad and small revelation of all that God is and does for us!
I believe that Luke's Gospel in certain ways contains greater revelation of Jesus than Matthew's, in part because Luke was a gentile writing to fellow Gentiles who were not under law. They were not blinded by the veil of Moses (2 Corinthians 3: ) and thus Luke offered a revelation of Jesus as the Son of Man, one who understands us on every point, one who understands our concerns, one who understands the every details of our lives. Only in Luke's Gospel do we read the parable of "The Prodigal Son". Only in Luke's Gospel do we witness Jesus' ministering to one of the thieves on the Cross. Only in Luke's Gospel do we find the example of reading and seeing Jesus as the central theme of all Scriptures (Luke 24: 25-27)
From this revelation, then we see Jesus as God, as He who has been from the beginning. King, servant, and in the form of man, yes — but above all God, in the beginning and the one who made all things.
John's Gospel is written also by one who had the deepest revelation of God's love, of Jesus' love, for him. When you see Jesus as God, fully King yet fully close to you, fully serving and understanding you in every point, then you will understand His love, and He will live in you in full grace and truth.
I cannot stress this enough — I do not disparage the four Gospel writers, per se. Yet I do realize that each writer as a different vision of the Lord Jesus, and as one reads from one Gospel to the next, the revelation of Jesus expands through the power of the Holy Spirit until we come to John's last words:
"And there are also many other things which Jesus did, the which, if they should be written every one, I suppose that even the world itself could not contain the books that should be written. Amen." (John 21: 25)
John had the final vision of Jesus who does beyond what we ask or think (Ephesians 3: 20). The greater your revelation of Jesus in grace and knowledge, the greater His power and glory will manifest in your life, too.