The wave in the title of Sonali Deraniyagala’s new memoir might be a metaphor: When misfortune strikes, it crashes into and washes through our lives, then back out again.

But the wave here is deadly literal: the tsunami that devastated Southeast Asia the day after Christmas 2004. That morning Deraniyagala, a London-based, Sri Lankan-born professor of economics, was vacationing with her family on the southeastern coast of her native island.

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To no avail, they attempted to escape the 30-foot wave in a jeep, which was overturned by the “charging, churning” water. As Deraniyagala was swept away, she reached out for and clung to a branch. When she found her feet on firm ground again, her family was gone — husband, two sons and both parents. Unlike the 2012 film about the tsunami, “The Impossible,” there is no Hollywood ending here.

But this natural disaster, made chillingly real in Deraniyagala’s spare prose, is just a prologue to the real story: the author’s life in its aftermath. She spends months in a darkened bedroom at her aunt’s house, plotting to kill herself. She drinks recklessly — vodka, wine, whiskey — in order to fall asleep at night, knowing she “had to wake up the next morning and relearn the truth all over again.” When a Dutch family rents her parents’ abandoned home, she begins to torment them, ringing the doorbell at all hours and making crank calls. She is not a noble widow.

Almost four years after she left it, Deraniyagala returns to her London home, frozen in time; a pile of unopened Christmas presents awaits the children’s return. Gradually, she sketches in portraits of her husband, Steve, and the boys, Vikram and Malli; they become not casualties but characters. “I have learned that I can only recover myself when I keep them near,” she writes.

Like Joan Didion’s “Year of Magical Thinking,” “Wave” captures the elusive, shape-shifting nature of grief. There are no self-help lessons here, only the story of a woman who finds a way to live when her loved ones have died.