The Gospels are not abstract theological treatises or collections of moral guidelines. Rather, they are narratives that proclaim the Good News of our salvation by recounting the story of Jesus of Nazareth, whose life, death and resurrection are the foundation of our Christian way of relating to God. They are also our chief resources for learning who Jesus was and what his mission was. [For a more detailed consideration of this see my book Who Do You Say I Am? The Catechist’s Guide to Jesus in the Gospels (Faith Alive Books, 2015)].
Moreover, although the Gospels are often represented as documents that we might use to invite others to become followers of Jesus—to evangelize as we say today—a careful reading reveals that the Gospels would be very hard to understand without some familiarity with Jesus’ story and his expectations for his followers. In other words, the Gospels were not written to convert outsiders but as catechetical documents to deepen the faith of those who have already committed themselves to Jesus and his community by adopting his vision of the world, his values for living in it, and the vocation to continue his mission of bringing the Good News to others.
So What's the Good News? The Catechist's Guide to Reading the Gospels by Steve Mueller. p 2.