From Montgomery and Cosper's excellent book, Faithmapping:
The gospel of God's grace is the wonderful news that God accepts us and shares his life with us not because we have earned or deserved it but because he gives it to us freely at Christ's expense.
Understood biblically, grace is nothing less than a scandal, and it's a message that insults and offends the consciences of religious people of all stripes. At the heart of religion is a belief that, properly performed, religion makes us acceptable before the eyes of God. Grace shatters that idea. It says we can never perform up to God's standards, but in Jesus, God has miraculously loved and accepted us anyway.