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)
Mom is kind of nuts.
The book's early scenes establish Jack's relationship with his mom, the fact that they move around from place to place, and Jack's need to make up stories about himself. We learn that Jack's mom dates serious losers, and some of them come after her in ways that would get them slapped with at least a restraining order in this day and age. This is mostly preamble, which gets us up to speed on Jack and his mom, showing us how they interact with each other (mostly by mom letting him get away with too much), and giving us a taste of Dwights to come with Roy. Once we're braced with the details, Wolff can move forward with the real fireworks.
Rising Action (Conflict, Complication)
Wicked Stepfather
The rising action fills up the bulk of the story, as Dwight marries Jack's mom and immediately sets out on a delightful pattern of verbal insults and borderline beatings. Jack struggles to find out who he is—adopting different poses or false fronts while search for ways to feel at home with himself—while fending off Dwight's half-baked plans and loose fists. The situation gets worse and worse, increasing the tension to a point where somebody pops. In this case, that means the loose fists get a whole lot tighter.
Climax (Crisis, Turning Point)
A Beating too Far
Things finally go overboard when Dwight shoves Jack and forces him to land on a badly injured finger. Jack's mom puts her foot down and makes a direct route for the exit. Suddenly, the biggest obstacle to Jack's happiness has been removed and the conflict between Dwight and Jack is resolved with a technical win for Team Jack. Dwight's gone, story's over.
Falling Action
The Consequences.
Or not. Jack still has to deal with the kinds of wounds Dwight left—the kind that don't heal—while making sense of his new situation. It's a messy process that involves almost losing his foster home, getting kicked out of prep school and drinking more than a lad of his age should. The falling action shows us how life with Dwight has affected Jack, and how the struggle to find himself continues even when the psychotic Scoutmaster isn't pounding him into the pavement.
Resolution (Denouement)
Nothing Ever Ends
Since it's a biography, there's no "he lived happily ever after." Jack's life goes on just like everyone else's, so the book doesn't end so much as find a convenient place to stop. Wolff talks briefly about what happens to him after Dwight, and implying that more bad things are coming with the Vietnam War.
Then, having said that, he rolls back the clock a little bit to talk about him and his friend Chuck driving home to Seattle. They're hopeful and upbeat about the future: "we both had cause to rejoice and this helped us imagine we were friends." (31.17). He wants to end things on a happy note without letting us forget that life goes on and this isn't really the end (for better or for worse). So… we get a moment when things are happy and a reminder that things will get less happy soon. A decent place to end, considering the circumstances.