As good and succinct an answer as I’ve found to the question, “What is the gospel?”:
The gospel is this: We are more sinful and flawed in ourselves than we ever dared believe, yet at the very same time we are more loved and accepted in Jesus Christ than we ever dared hope. This is the only kind of relationship that will really transform us. Love without truth is sentimentality; it supports and affirms us but keeps us in denial about our flaws. Truth without love is harshness; it gives us information but in such a way that we cannot really hear it. God’s saving love in Christ, however, is marked by both radical truthfulness about who we are and yet also radical, unconditional commitment to us.
Tim Keller, The Meaning of Marriage, 48.