The book, according to Joseph Fitzmyer, "overwhelms the reader by the density and sublimity of the topic with which it deals, the gospel of the justification and salvation of Jew and Greek alike by the grace of God through faith in Jesus Christ, revealing the uprightness and love of God the father." N.T. Wright notes that Romans is "neither a systematic theology nor a summary of Paul's lifework, but it is by common consent his masterpiece.
Paul's Epistle to the Romans dwarfs most of his other writings, an Alpine peak towering over hills and villages. Not all onlookers have viewed it in the same light or from the same angle, and their snapshots and paintings of it are sometimes remarkably unalike. Not all climbers have taken the same route up its sheer sides, and there is frequent disagreement on the best approach. What nobody doubts is that we are here dealing with a work of massive substance, presenting a formidable intellectual challenge while offering a breathtaking theological and spiritual vision".
I. The doctrinal part of the epistles instructs us,
1. Concerning the way of salvation (1.) The foundation of it laid in justification, and that not by the Gentiles’ works of nature (ch. 1), nor by the Jews’ works of the law (ch. 2, 3), for both Jews and Gentiles were liable to the curse; but only by faith in Jesus Christ, ch. 3:21, etc.; ch. 4. (2.) The steps of this salvation are, [1.] Peace with God, ch. 5. [2.] Sanctification, ch. 6, 7. [3.] Glorification, ch. 8.
2. Concerning the persons saved, such as belong to the election of grace (ch. 9), Gentiles and Jews, ch. 10, 11. By this is appears that the subject he discourses of were such as were then the present truths, as the apostle speaks, 2 Peter 1:12. Two things the Jews then stumbled at-justification by faith without the works of the law, and the admission of the Gentiles into the church; and therefore both these he studied to clear and vindicate.
II. The practical part follows, wherein we find, 1. Several general exhortations proper for all Christians, ch. 12. 2. Directions for our behaviour, as members of civil society, ch. 13. 3. Rules for the conduct of Christians to one another, as members of the Christian church, ch. 14 and ch. 15:1-14.
III. As he draws towards a conclusion, he makes an apology for writing to them (ch. 15:14-16), gives them an account of himself and his own affairs (v. 17-21), promises them a visit (v. 22-29), begs their prayers (v. 30-32), sends particular salutations to many friends there (ch. 16:1-16), warns them against those who caused divisions (v. 17-20), adds the salutations of his friends with him (v. 21-23), and ends with a benediction to them and a doxology to God (v. 24-27).
Henry, Matthew. "Introduction to Romans."
→ Yale University: Paul’s Letter to the Romans