Most good stories start with a fundamental list of ingredients: the initial situation, conflict, complication, climax, suspense, denouement, and conclusion. Great writers sometimes shake up the recipe and add some spice.
Exposition (Initial Situation)
Let's Start at the Very Beginning, A Very Good Place to Start
Where else to begin but when you were born? Augustine's life of miserable sinnin' begins at birth, you know.
Rising Action (Conflict, Complication)
Being Bad Feels So Good
The older Augustine gets, the more sins come his way. Lust, theft, lust, pride, lust, Manichaeism, lust… the list goes on. This section starts around Book III, when Augustine goes to the Sin City of the Ancient World, a.k.a. Carthage. That's when Augustine enters into adulthood, and can't chalk up his antics to boyish tendencies anymore.
Climax (Crisis, Turning Point)
"I want the truth!" "You can't handle the truth!"
But all is not well in Augustine-town, because pretty soon, he starts to question the logic of Manichaeism and wonder why he is so miserable. This is around the time he goes to Italy, toward the end of Book V, and starts to learn about the Scriptures from Ambrose. The big climax is, of course, the moment of his conversion to Christianity at the end of Book VIII.
Falling Action
Stairway to Heaven
Just because Augustine converts doesn't mean that life is now puppies and rainbows. He still has to learn to deal with all of his sinful tendencies, which haven't gone away. The aftermath of his conversion is described in Book IX, and his personal handbook on how to deal with pride and wet dreams is in Book X.
Resolution (Denouement)
Genesis 101
What do good Christians do? They read the Bible, of course. By "read the Bible" we really mean "read the first chapter of Genesis." Augustine basically pulls an Old World Shmoop and analyzes the first few lines of Genesis for his readers in Books XI to XIII, so that we can better understand them. He hopes that all this 'splainin' he has done will earn Christianity some new converts. He's come a long way, that Augustine.