One of the most annoying things a reviewer can do is to call something "deeply human." What else would it be, after all? One suspects everything created here on planet Earth by Homo sapiens sapiens is sufficiently humanoid to qualify, and "deeply" is just another example of our over-reliance on adverbs. But that's how I want to describe My Real Children—a deeply human narrative of a woman's twinned lives, the fragile balance of love and loss she achieves, and the choices we all make that can't be unmade.

This is a story that begins at the end: it's 2015, and Patricia Cowan is an old woman. She leads the undignified life of a patient suffering from dementia in a nursing home, with caretakers who leave sticky notes tacked to her bed about her mental state: "Confused Today," or "Very Confused." Pat gets confused about the little things, like whether she took her pills and when she ought to sleep, but she also gets confused about the most fundamental facts of her life. She seems to remember having three children, but also having four. She remembers having a husband and also never marrying, Kennedy being assassinated and Kennedy retiring from politics, living in Florence and living in the suburbs. She has two overlapping sets of memories, and she can't remember which one is real, and which children are her real children.

The rest of the book is the narrative of Pat's entire life—twice over. Her memories split in the spring of 1949 when a promising young scholar named Mark proposes marriage to her. In one memory, she says no. In the other, she says yes. From that single point her lives spread out in fractal patterns, sometimes resonating between each other but more often diverging.

In the universe where she said yes, Pat finds herself trapped in the special hell of an unloving marriage in the mid-twentieth century, bound to household drudgery, childbirth, and isolation. It's frankly terrifying, and all the more chilling for its banality.

In the other universe, where Pat told Mark exactly where he could shove his 1950s dream-marriage—ahem, where she said no to his proposal—things are brighter. Pat leads the bold life of an educated single woman and eventually falls in love with the clever and dear Bee. I loved their life together, existing in the liminal gray areas of British marriage and family structures.

Both lives end up in the same place: alone, confused, in a nursing home. And both lives are equally real. The whole time you're waiting for the curtains to close, for the edges of the story to draw in and wrap Pat's life in a neat bow, but it never happens. This is her whole life, beginning to messy middle to inevitable end. And while one reviewer made the not-inaccurate comparison between My Real Children and reading a series of family newsletters at Christmas, I've never been so moved by a family newsletter.

It's difficult to articulate why. This isn't a maudlin series of Sophie's Choices, relying on the tension of misery. And it isn't exactly action-packed. We spend a lot of time doing things like looking at Italian Renaissance sculpture, and birding in the countryside (is there anything duller than birding? Maybe stamp collecting), and joining anti-war campaigns. But there's something about the dual narratives that renders even the most mundane elements desperately important. It's the simple tension of not knowing what is real, and what might be casually wiped away.

My Real Children is also, necessarily, a history of the twentieth century. Or, more accurately, two histories of the twentieth century. The life where Pat marries Mark resembles reality. No nukes are ever dropped during the Cold War, Civil Rights sweep across the globe, and we slowly slide away from the brink of mutually assured destruction. In Pat's life with Bee, the Cold War becomes a real war. The world becomes uglier, harsher, and more likely to implode at any second. If nothing else, these alternate histories are powerful meditations on the significance of the 1960s and 70s and the populist efforts towards peace and human rights.

It's a terribly romantic book, too, but not in the way that alternate-universe books usually are. This isn't about finding your One True Love No Matter the Obstacles. At some point Pat comforts Bee by telling her "No matter what happened, we'd have found each other" (p. 108). It's a uniquely sad feeling, hearing a lover say that and knowing it's not true.

But still, the defining decision in Pat's life is about who she loves. It would not surprise me if there were readers who disagreed with that—would a marriage proposal really determine the nature of a woman's entire life? Who is she independent of Bee or Mark? Walton seems to feel that our lives are only half-made by us; the rest of us is sculpted by the people nearest to us, and god help you if the people nearest you are cold or cruel or ham-handed.

But none of those things are the reason you finish the book and end up crying into your coffee mug and blubbering incoherently to your partner ("It's just—life is full of these choices, you know? And like, I love you, and it’s just so sad"). My Real Children's true power is intimate and reflective, occurring more in the reader’s brain than on the physical page. See, My Real Children leads a double life; it's a book, but it's also a mirror.

Every single person has pivotal moments in their pasts—the points when our lives split like dividing cells, and the endless might-have-beens of our DNA were suddenly erased. My Real Children invites us to wander down the illusory spiderwebs of our own pasts, to find our own breaking points. And through some strange, transitive process, Pat's divergent lives become our own. We live her successes and failures, her fragile joys and miseries, and find both to be terribly fleeting.

Bee confesses, late in their lives, that she "used to think we had time to do anything we wanted, but we can only do some of the things in any one lifetime." And Pat quotes Andrew Marvell's poetry in response: "But at my back I always hear time's winged chariot hurrying near. And yonder all before us lie deserts of vast eternity" (p. 252). More than anything else, this is a book about the deeply human fear of time's winged chariot.

Alix E. Harrow teaches history and posts speculative fiction reviews on her personal blog. She lives in a romantically dilapidated farmhouse with her partner in Kentucky.