Romans

The book of Romans was originally directed toward believers in Rome. Paul wrote it mainly to give the Romans a concrete and solid foundation for their faith. The book of Romans told them that they should live and serve God to the fullest. Romans can both lead many people to Christ and strengthen many Christians in their faith. One main theme throughout the book of Romans is the focus of "The righteousness of God." Paul explains how salvation isn't obtained through doing good things but is obtained through faith in God's righteousness. Even today, the book of Romans is still applicable for believers and is still a great source in the Bible to lead others to Christ.

The hardest thing out of Romans to explain to non-believers would be the whole concept of faith in God. This would be hard to explain because most would be confused why you would need faith in somebody or something that is not physical. This would especially be hard to explain to an atheist. The most believable or sensible thing to a non-believer would be to explain that there is a God that loves them but all your sins would separate you from Christ.