After reading a paragraph, a chapter, or a whole book, are you able to turn around and summarize what you’ve just read? It’s a great practice to jot down notes in the margins as you read, just as a simple exercise to make sure you’re actually processing the words that pass before your eyes. Then on the larger scale, we should ask ourselves the obvious questions after the completion of a book, “What did I just read?” Here is a short attempt at answering the question in a more roundabout way from the site Near Emmaus. He is attempting in just a couple paragraphs to describe the reason that Paul wrote Romans, and in so doing gives broad strokes of description about the whole book.
Here is just one line, but go to the site for more:
This epistle addresses the Adamic problem including Jews and Gentiles. Paul uses this problem to show the glory of the salvation found in those who have followed Abraham’s model of faith which is now encapsulated in those who call Christ “Lord”.
Give it a shot yourself after a chapter or section. See if you can very briefly boil down some of Paul’s arguments as you read. It’ll help you to better understand and retain these words of Scripture.