The Gospels are an authoritative commentary on the Hebrew canon.

They are a commentary

The gospels do not stand alone. If only the gospels are read, the question is "So what?"

So what if a man claimed to be the Son of God? Lot's of men do.

So what if he taught 'novel things'? Lot's of men do.

So what if he died on a cross? Lot's of men did.

The gospels are a commentary on the life of Christ showing that he fulfilled the prophecies of the Hebrew canon. The God of the Hebrews said he would do things in riddles/mysteries and the gospels reveal the mystreries:

Ro 16:25 ... the preaching of Jesus Christ, according to the revelation of the mystery, which was kept secret since the world began...