“Monogamy,” by Sue Miller (HarperCollins)

Even after reading all 338-plus pages of Sue Miller’s new novel, it’s hard to tell if the noun of the title is aspirational or unattainable. And maybe that’s the point.

“Monogamy” stars Annie and Graham, two Cambridge residents devoted to the arts (he co-owns a bookstore, she’s a photographer), happily married for three decades. Miller shifts timelines — a memory in the present sparks a pages-long trip into the past where we learn both of their back stories and get to meet the other people in their lives. They have one child together, Sarah, and Graham has a son from a previous marriage, Lucas. Friends flit in and out of the book just as they do in real life, filling out the main characters and making them come truly alive.

It’s not a spoiler since it’s right there on the book jacket, but the book turns on Graham’s unexpected death. He simply goes to bed one night and his heart stops beating. “Something essential to Graham, to everything Graham was, wasn’t there any longer,” writes Miller as Annie wakes up beside his body in the morning.

Graham’s death really jump starts the novel. As Annie mourns and begins to learn she didn’t know everything about her husband and his appetites, Miller goes deep inside her head, surfacing repressed memories and writing eloquently about grieving: “It seemed connected to the loss of Graham and her almost daily fear of losing him further, in memory… Could you will it the other way too, memory? Could you make yourself hold it, as much as you could make yourself lose it?”

Miller’s gift as a writer has always been finely drawn portraits of families and that talent is on full display here. We get chapters inside each character’s head, rich with details and inner monologues. Here’s Frieda, Graham’s ex, reflecting on her life as she rides the train home after caring for her new grandchild: “This was how you did it, she thought. How you managed in life. … These last days, holding the baby, singing to her. … All in the service of some sense of…what? Purpose, she supposed. Order. Or loveliness. A sense of loveliness that made everything possible. Why shouldn’t you have to work to hold on to it?”

There are tenderly realized moments like that throughout the novel, as Annie learns to live without Graham, eventually picking up her camera again in an attempt to preserve memories. She never truly wants to let Graham go, as if, in the end, that’s what monogamy really means.

It’s a beautiful book for a fall afternoon during this time when family means more than ever.