What is the good news of the Kingdom? Jesus said, "The Kingdom of God is within you." WITHIN you because you are created in the image and after the likeness of your God, our Father in Heaven. He has put His spirit WITHIN you. As a human being, there's a "Holy of Holies" WITHIN you. That's where the Father's spirit dwells. This is the true meaning of Job 32:8, "But there is a spirit in man..."
Jesus' gospel placed a central FOCUS on this very fact. Jesus did not say the Kingdom was about to come into you. No! He said it was already WITHIN you! Salvation comes to you when you believe and receive this fact by faith through the grace of God and dedicate your heart completely to walking in its realities again by faith through the grace of God. And then in intimate fellowship with God's indwelling spirit, you begin to manifest the values, character and culture of the Kingdom. As a result, the Kingdom would exert its influence in your midst or around you. This is how the kingdoms of men become the Kingdom of our God and His Christ.
This is a summary of the good news or the gospel of the Kingdom as presented by Jesus Christ. Anything different is "another gospel". It doesn't matter who presents it: be it an angel, Paul, Peter or your Pastor. It is "another gospel".