For a three-act plot analysis, put on your screenwriter’s hat. Moviemakers know the formula well: at the end of Act One, the main character is drawn in completely to a conflict. During Act Two, she is farthest away from her goals. At the end of Act Three, the story is resolved.
Act I
We don't have too much backstory yet, but we can tell early on that there is tons of pain running under of the surface of the Kashpaw family. The book opens with some details of June Kashpaw's final day on earth, which she spent barhopping with a strange guy rather than coming directly home to her family (as she'd originally planned). She ends up dead that evening, though the particulars are never really revealed.
The book then zooms back to the 1930s and works its way through the years immediately following June's death, which means we get the deep background on June's family and then the aftermath of her death. However, don't go thinking everything revolves around June—this story expands pretty quickly into being about the entire family.
The earliest section of these chapters chronicles the backstory of how Marie and Nector, June's initial guardians, got together and started a family. We also learn about a woman named Lulu Lamartine, who (because she was Nector's first love) ends up being pretty important, too.
Act II
After years of raising a family with Marie and working hard, Nector suddenly decides that he wants to hook up with Lulu again. So, that's what happens—and they sneak around together for about five years. Eventually, though, things come to a head when Nector decides he's going to leave Marie for Lulu. That plan never really comes off, but his attempt at making a permanent move to Lulu ends up with Nector accidentally starting a fire. So, he goes back to Marie, and Lulu marries Beverly Lamartine (her ex-brother-in-law).
Also, we get lots of about Lulu's life, her husbands/lovers, and her children. Her family has definitely had more than its fair share of tragedies. Her husband Henry committed suicide, and sadly his namesake (but not biological son, as it turns out) followed in his father's suicidal footsteps when he returned from Vietnam.
Act III
Nector's memory worsens, and he eventually dies in a retirement home. After his death, Marie and Lulu end up becoming friends and even mourn Nector together.
Meanwhile, Lulu's grandson, Lipsha, finally finds out that June was his mother—and Gerry, Lulu's son, was his dad. He ultimately seems pretty jazzed about finding out some more details about his origins and resolves to see his dad (who has been in prison off and on for years). That meeting does come to pass, and Lipsha even ends up helping his Pops flee the country so he can once again evade prosecution. And with that, we get a (kinda-sorta) happy ending,