There is little doubt that the book of Romans is one of the most influential books of the New Testament (NT). The book focuses on the heart of Christianity: salvation through the sacrifice of Christ (3:23-24), salvation through faith and not works (3:28), and that worship is a sacrificial act on our part (12:1).
Romans was written by Paul. Not only is this made evident by the fact that the author names himself 'Paul' in the first verse (indeed, fist word) of the book, but the writing and theology of the book is clearly Pauline. Paul wrote Romans sometime around the spring of A.D. 57. It is highly likely that Paul wrote Romans while travelling through Corinth and heading for Spain. Luke reports:
And Paul writes in Romans 15:24-26:
Moreover, in 1929, archaeologists unearthed limestone paving blocks in Corinth with the inscription: "ERASTVS PRO AEDILIT[AT]E S[UA] P[ECUNIA] STRAVIT" ("Erastus in return for his aedileship laid [the pavement] at his own expense"). An aedile was a comissioner of public works. Since "Erastus" is an uncommon name, it is likely that this was the same person as the person who Paul sends his greetings from (Romans 16:23).
Paul's epistles are ordered according to descending length in the NT. Thus, since Romans is Paul's longest epistle, it appears first. The central theme of Romans is salvation: salvation is a free gift of God received through faith alone. Romans may be divided into three sections. The first section (chapter 1-8) is chiefly the theological or doctrinal section. The second section (chapters 9-11) is an aside in which Paul discusses the rejection of the gospel by the Jews. Finally, the last section (chapters 12-16) focuses more on practical application.
Romans is a wonderful book, well worth the time to study it.