Tim Keller is one of my favorite authors/pastors - he has a way with meeting questions (and doubts) about Christianity that is patient, clear, concise, and most of all, loving and respectful. Two of his books have been greatly influential in my faith and theology: "The Reason For God" and "The Prodigal God." I highly recommend these to you.
In a 1993 sermon, Keller sums up Christianity:
Christianity is a way that says if you come to Jesus Christ, even if you aren’t good and decent, even if you aren’t wonderful, and even if you don’t have a good record, anybody through Christ can find God.
Somebody says, ‘How can that be?’ Let me just put the gospel in a nutshell:
because Jesus Christ lived a perfect life and died a perfect death, now God
treats you, when you believe in Christ, as if you have done everything Jesus
has done and you have suffered everything Jesus has suffered. God treats believing
sinners as if they had done everything Jesus has done and suffered everything
Jesus has suffered.
That means when you believe in Christ you’re
adopted not on the basis of your record, but on his record.
You’re adopted into
the family and treated as if you’d accomplished everything he’s accomplished.
That’s the gospel.
Somebody says, ‘It’s too easy.’ I don’t know how many times
people have said, ‘That’s just too easy. You mean you just receive it?’ Yeah,
but you have to receive it through repentance, and that’s what’s not easy at
all.
The only way to get to that peace is through paying the pain of
repentance. In other words, all you need is nothing, but most people don’t have
that.
(Tim Keller, 1993)
(Tim Keller, 1993)