WAVE. By Sonali Deraniyagala. Knopf. 228 pages. $24.

Sonali Deraniyagala’s memoir, “Wave,” begins where her trauma began, with a wave.

She writes, “I thought nothing of it, at first. The ocean looked a little closer to our hotel than usual. That was all. A white, foamy wave had climbed all the way up to the rim of sand where the beach fell abruptly down to the sea.”

It is the day after Christmas 2004. Deraniyagala and her family (parents; husband, Steve; sons, Vikram and Malli) have spent the holiday at Yala, a national park on the coast of her native Sri Lanka. In a story that still seems far-fetched to her all these years later, Deraniyagala’s family vanished in an instant. The wave came, they made a run for it, hopped in a Jeep, were flooded out, overturned and lost each other.

To tell a story of boundary-crashing chaos, Deraniyagala’s style is contained and still.

For the short time of the wave, everything becomes spectacularly what it’s not, but her prose is steady, never histrionic.

As her family’s only survivor, Deraniyagala recoils from a world without them. She spends her first year in a stupor, sampling varieties of obliteration: stabbing herself with a butter knife, drinking in a frenzy. When she finally gets up the courage to leave her room for a drive, where does she go? To torment the renters of her parents’ house, barraging them with phone calls and banging on their gate at 2 a.m.

These are not pretty scenes; but the savage truth of early grief sets the stage for the delicate truth of the ending. Deraniyagala structures “Wave” by the calendar. Each chapter stamps a point in time and space: from Yala, Sri Lanka, Dec. 26, 2004, to New York, June 22, 2012.

Each year marks a step away from isolation and back to her family.

Telling her story, Deraniyagala is the opposite of self-absorbed. Midway through the book, a friend of hers meets one of the men who rescued her from the wave.

Once out of the water, she still couldn’t stop spinning, he reported. The first years into her recovery, it’s as if Deraniyagala still is spinning, unsure where to look for balance. The outer world is booby-trapped with places and things that her family loved. How can she enjoy watching blue whales, she asks herself, when Vik will never get to see one?

The inner world is just as dangerous. There she’s ambushed by memories and guilt. The sad irony is that the very thing that will soothe her, remembering their happy life, is the thing that seems most unsafe.

Incrementally, Deraniyagala lets the past back in. In 2005, she goes back to Yala repeatedly and once finds the green shirt Vik wore on his last Christmas. Three years and eight months after the wave, she’s able to go back to their London house.

There, she finds an eyelash on Steve’s side of the bed. She begrudges her own sanity: “Every time I read about England winning a test match or about Pluto no longer being a planet, I loathe myself for not howling endlessly.”

Yet she doesn’t howl — far from it. Deraniyagala uses austere, beautiful language to resurrect her people. She lets us in to the ordinary routines of the family: her mother’s prawn curry, Steve’s Sunday evening shoe shines (the buffing rag alone could make her cry), Malli’s theatrics, Vik’s math wizardry, the silly family jokes.

In one reality they’re gone, but in another, they’re right here on the page. Deraniyagala’s book remains small and personal, a trimmed-down and invigorating testament to love.

Reviewer Catherine Holmes teaches English at the College of Charleston.