Romans

The treatise of Romans is part of the 'all truth' that Jesus Christ spoke about in John 16:13. In verses 7-11 that truth is laid out:

Nevertheless I tell you the truth; It is expedient for you that I go away: for if I go not away, the Comforter will not come unto you; but if I depart, I will send him unto you. And when he is come, he will reprove the world of sin, and of righteousness, and of judgment: 

Of sin, because they believe not on me;

Of righteousness, because I go to my Father, and ye see me no more: 

Of judgment, because the prince of this world is judged.

Three important subjects are covered in the seven church epistles: sin, righteousness and judgement. These are  the subjects of the great treatises, Romans, Ephesians, and Thessalonians that beautifully show what God has made us to be in light of the death, resurrection and ascension of His son.

Romans reproves the world of sin. Sin is the inattention to what God has done for us and the symptoms that result from that lack of attention. The recurring theme in Romans is believing in the grace and finished work of Jesus Christ.  Chapters 1-11 teaches about how the work of Christ has brought us to the place of also being called God's sons. Chapters 12-16 teaches how to practically live in light of this.

Ephesians is the treatise about our righteousness and a Father's love.

John 16:25-27 These things have I spoken unto you in proverbs: but the time cometh, when I shall no more speak unto you in proverbs, but I shall shew you plainly of the Father. At that day ye shall ask in my name: and I say not unto you, that I will pray the Father for you:For the Father himself loveth you, because ye have loved me, and have believed that I came out from God.

Chapters 1-3 of Ephesians specifically teach  about our righteousness, while chapters 4-6 is about how to practically apply it.

Thessalonians is about the hope, our future as believers lifted out from the present world and its dominions and spiritual lawlessness. It points to the eventual return of Jesus Christ.

The book of Romans is absolutely essential for our freedom in this life. It lays the foundation for living a life that honestly glorifies God. God has always desired to have a relationship with man. It started in Eden. Adam and Eve decided to ignore God's instructions and fell.  Jesus Christ took the fall and got up so that our relationship with God could be on a permanent basis. Ignorance is not bliss in this case. Romans is a book to pay attention to.