This book, probably better than any other, gives the essence of the gospel. Man is sinful, but God saves on the basis of grace. Man can never do enough, but God has provided all that is needed for the one who believes. Some might think that because the Jews aren’t believing that they have been rejected from God’s plan, but Paul explains why this is not so (chs. 9-11). As in most of his books, he concludes with practical advice on how to live. One interesting thing about Romans is that Paul had never been to the city when he wrote this letter. Yet note how many people he knows (ch. 16).
If you prefer more detail, here is the summary of the book from my argument:
The letter to the Romans is a bold and clear statement of the gospel of Jesus Christ. The beginning of the letter is primarily concerned with truths of salvation and the conclusion of the letter focuses on the practices that should be manifest in the lives of believers as a result of these truths. As Paul states in the introduction, the gospel is indeed the power of God for salvation, and he develops how this is so first by declaring man’s universal need for salvation by virtue of being under the power and condemnation of sin. Deliverance is offered to all but only on the basis of faith in Christ’s substitutionary atonement. This principle of salvation by faith is not new but has been God’s means of working since the time of Abraham. The result of being justified by God is peace with God, a reality possible by virtue of union with Christ and his distribution of life to all who are in him. Those united to Christ are free from the condemnation of sin and the power of the law so that they can live victoriously by the Spirit.
Paul emphasizes the assurance that believers can have based upon God’s past work and his future promises. These are not negated by Israel’s rejection of Christ, but rather are explained as typical of God’s sovereign purposes and the nation’s unwillingness to submit to the righteousness of another. God’s promises will indeed be fulfilled in the nation of Israel following the ingathering of the Gentiles when all Israel is redeemed and forgiven. Given the abundance of God’s mercy poured out, believers must live in righteousness and love both towards one another as well as to outsiders. Jews and Gentiles in the church must not reject those whom Christ has accepted but love one another without passing judgment or causing believers to sin. Paul anticipates his arrival in Rome following his visit to Jerusalem and he looks forward to his fellowship with those who have now heard the gospel he preaches.
Romans “gives the essence of the gospel”, & it’s worth noting to casual Bible readers that Paul probably wrote it before any of the 4 gospels were published.