I could recommend a number of his books. He makes the case for the reasonableness of the Christian faith in 'The Reason for God'. He highlights the mercy that should characterise the Christian life in 'Generous Justice'. He teaches how to grow to be godly in marriage in 'The Meaning of Marriage'. He exposes the idol of self in 'The Freedom of Self-Forgetfulness'. He shows the beauty of grace in 'The Prodigal God'. In the book club that I go to we will be soon looking at his book 'Walking with God through Pain and Suffering'. But the book I wish I could force every young and old adult in our church to read is his teaching on the first half of the apostle Paul's letter to the Romans (please get yourself a copy).
Anyway, I include this clip of Tim explaining the gospel.