Just as the events of Sept. 11. 2001 took a few years to percolate into fiction, so, too, has the COVID-19 pandemic.

It’s no wonder that it’s now featuring so prevalently. Lockdown — such a cataclysmic, scary, and unprecedented global event — offers rich possibilities to the writer, both dramatic and metaphorical.

Michael Cunningham’s Day joins a recent wave of pandemic novels that includes Ann Patchett’s Tom Lake, Chris Bachelder and Jennifer Habel’s Dayswork, and Sigrid Nunez’s The Vulnerables, to name a few favorites.

Structured as cleverly as a well-made play, Cunningham’s first novel since The Snow Queen was published nearly a decade ago zooms in on a troubled, extended Brooklyn family on the fifth day of April in three consecutive years: 2019, before the pandemic disrupted life as we knew it; 2020, during the unnerving early months of lockdown; and 2021, after the worst fear had passed. The novel’s first act is set in the morning, its second at midday, and its third in the evening.

Cunningham is best known for his superb 1999 Pulitzer Prize-winner, The Hours. An inspired take on Virginia Woolf’s Mrs. Dalloway that was recently adapted into an opera, Cunningham’s fourth novel is set during a single day leading up to a party. Day, his eighth, moves inexorably towards a very different sort of celebration.

But while ingeniously conceived, Day strains to hit the high notes of The Hours. The biggest obstacle is its characters. It is hard to engage and fully empathize with their problems, which are mainly late 30-something disappointments that life is not living up to expectations. More problematically, the two school-aged children and their reflections don’t ring true to age, even for precocious New York City kids.

Nathan and Violet, 10 and 5 at book’s start, are the offspring of Isabel Walker, a photo editor whose job at an artsy print magazine is soon to become extinct, and Dan Byrne, a former minor rock star and recovered addict who is “sweetly delusional about his prospects” for launching a comeback. For the time being, Dan has cheerfully agreed to play “the harried servant” to the kids. He is doing his good-natured best as Isabel drifts away from them all.

Virtually every New York City story is a story about inadequate, unaffordable real estate, and so is the Walker-Byrnes’. They live in a cramped two-bedroom Brooklyn rowhouse apartment they’ve outgrown. The most practical solution is to move their son up to the finished attic, which they’ve long rented to Isabel’s gay brother, Robbie.

But Robbie, also in his late 30s, is an adored extra parent to the kids; he’s close with his sister and even closer to Dan. Recently broken up with his boyfriend, he can’t afford anything remotely habitable nearby. He’s starting to regret having turned down medical school acceptances 15 years earlier in order to teach sixth grade history in NYC’s challenged public schools — a calling that is wearing increasingly thin. “It’s time to abandon a life of reasonable expectations. It’s time to be more interesting to himself,” he thinks.

Robbie is actually the novel’s most compelling character, certainly more interesting than Dan’s attractive but irresponsible younger brother, Garth, a sculptor whose career hasn’t yet taken off in 2019. To Garth’s surprise — and that of the lesbian college friend, Chess, for whom he agreed to be a sperm-donor — he is enchanted by their infant son, Odin. Unfortunately, Chess has trouble conveying to Garth that she has never wanted a man in her life.

Day is best appreciated on the structural and sentence levels. Cunningham writes beautifully, and pulls off one sharp observation after another. He certainly understands sibling rivalry: After a to-do at breakfast when Violet spills juice on her brother’s pants, “Nathan eyes her murderously.” As for the increasingly disengaged Isabel, her white blouse is “unbuttoned to the buttonhole that separates dignity from display” as she heads toward work on April 5, 2019. Mortified to find herself weeping in the subway, she is upset about “her ever less successful attempts to impersonate a mother” — and her 5-year-old daughter’s ability to recognize that she’s faking it.

One pivotal character in Day is a perfect match for Robbie, a 30-ish gay pediatrician named Wolfe who is “ready to commit.” The trouble is, Wolfe isn’t real; he is the outgrowth of a shared fantasy from Isabel and Robbie’s childhood. Wolfe has come to embody an escape hatch for them — and they are not the only ones charmed by his perfect life: Wolfe’s daily activities, shared in frequent Instagram posts, have garnered 3,407 followers and constant “likes.”

One doesn’t read Cunningham for the plots, but even so, I don’t want to give away what happens to this family when the pandemic hits. What I can say is that you see at least one development 2,600 miles away — the distance between New York and Reykjavik, where a character gets stuck during the height of the pandemic. Letters written from a remote Icelandic cabin bear what are perhaps unintentional echoes of Chris McCandless, the subject of Jon Krakauer’s Into the Wild.

Day (like Stephen Sondheim’s “Merrily We Roll Along”) is a sad story of middle-aged disillusionment. It’s about losses that range from a “low howl” to the unbearable. It’s about the belated end of blithely delayed maturity and the premature end of childhood. But it’s also about taking stock and making changes before it’s too late. It isn’t without hope.