At least one early review of Graham Swift’s “Tomorrow” (Knopf, 272 pages, $23.95) complained that it was suspenseful to the point of being contrived. A middle-aged mother, Paula Hook, is lying awake while her husband sleeps. In the morning, by agreement, they will reveal a crucial secret to their 16-year-old twins. Paula worries; she considers this the end of family life as she has known it. But her interior monologue doesn’t get around to the secret itself, at least not explicitly, until nearly the end of the novel. Like Susan Minot’s “Rapture” (2002), which takes place during one act of oral sex, Mr. Swift uses this one wakeful night to explore a lifetime of memory. Paula’s mind reverts, automatically, to her first night with Mike — their secret is somehow sexual, or one of paternity, we surmise. Her recollection of that first night is emphatically positive:

“. . . We were engaged in a wonderful, slow, wave-like motion that neither of us wanted to stop. We were making love, but we were also falling, falling in love. It’s possible, I assure you, for the two things to happen at once. I’m the proof.”

Who is Paula trying to assure? Her children — these ruminations are addressed to her children, in all of their sexual awkwardness. “You haven’t even begun the process,” she reasons, “of finding someone to sleep with.”

A strange book, you might say, in which a mother bombards her children with sexual confessions while withholding the one secret that keeps us turning the pages. But to leave it at that would be to miss the point of Mr. Swift’s narrative style.

Most of Mr. Swift’s books, including “Waterland” and the Booker Prize-winning “Last Orders,” have adopted a similar narrative frame. A short, sharply-defined narrative in the present becomes a window on decades and decades of the past. “Waterland,” for example, focuses on a single lecture by a sacked English instructor, but also brings in more than 200 years of East Anglian history, as well as the story of the instructor’s marriage.

The particular strength of that style, in “Tomorrow,” is that the narrator’s audience isn’t present. Although Pauline addresses herself to her children, they will simply never hear this internal monologue. Their ostensible presence shapes her story — though Paula is free among her own thoughts, the idea of her children brings delicacy and suspense to what would otherwise be a ramble.

“You came from happiness, my darlings.” Paula wants to make sure the twins know they are loved, even while she chops down their family tree and sketches a new one. Happiness equals destiny, is the modern assumption, and if Paula can assure the twins — and herself — that the members of this nuclear family were meant for each other, then the technicalities of birth won’t matter.

From her first date with Mike — lunch on the beach, after a night in bed — Paula was already telling herself a story about inevitability. “By that third bottle, if your father had told me that he’d planned that day long in advance . . . I would, of course, have utterly believed him.” Mr. Swift reminds us that stories of certitude are always present when we are trying to reassure ourselves about love.

The technicality, the “unexploded bomb,” as she calls it, that will compromise Paula’s children in the morning gives Mr. Swift opportunity to test the very idea of family. How much does genetic relation matter? Would a genetically-modified baby be truly yours? Is family about genes, or about possession? What about fate? What if you fall in love, as if by destiny, with an unfertile person? What if you then have children by other means? Are your children still “meant to be?”

These meditations come to life with Paula’s narration. She is sweet, but also very worried, and she carries a burden of suspended relief through this quick novel. The way she talks about time, constantly comparing the 1960s to the 1990s, as if she were amazed by how time had grown, gives her a certain doting stature. “This was in the late 1960s and, yes, they’re ages ago now.” She recalls the first time one of her children said, “Tell me about before I was born.” This is the question she will finally have to answer in the morning.

The distinction between mere existence and full autobiographical knowledge fascinates Paula. She remembers when her children were babies, “still deep in that time before you met your memory — or the one we gave you.” The same could almost be said of her babies at 16, sleeping elsewhere in the house, unawares. Paula, the creator of children as well their identities, becomes a kind of guilty Prometheus.

“Tomorrow” is a slender masterpiece. Gimmicky as its premise may sound, it is one of the more profound novels to be published this year.

blytal@nysun.com