A tricky book to categorize, O’Farrell’s family saga examines the elusive territory of experience and how people and events imprint us when we're young then linger, exerting subtle pressure over how we live our lives. Homemaker Gretta lives with her husband, Robert, in London, but she’s somewhat estranged from her grown children: Monica, Aoife, and beloved son Michael Francis.

Since his retirement, Robert has become brooding and bored. Gretta calls his name, unprepared for his sudden disappearance outside their suburban home, an event that becomes the background against which the larger story unfolds. This is London in the heatwave of 1976. The softening tarmac and choked roads and the burnt grass of Clissold Park add to the scorched, parched landscape that is both physical and metaphorical.

Tortured Michael Francis represents this principle in action, a man so conflicted that, when we meet him, he’s literally choking in the unintended heat of his family life. He hurries home to a wife who will no longer look him in the eye, who no longer seeks his touch and “whose cool indifference” provokes him to a low-burning, low-level panic. His sister Monica almost certainly shares that perspective as her life also unfolds in a kind of double vision and a marriage that seems to have lost its way.

O’Farrell uses Robert’s disappearance as a catalyst to show us attributes her characters are not yet ready to understand, whether this has to do with Aoife’s hipster life in New York or the more complex insecurities of Monica, who aches to be free from her dreary antique-dealer husband. While Gretta remains stalwart that Robert has not actually deserted her, Michael Francis requests that Monica come to London to help their mother and contact Aoife. The imminent reunion reinforces Monica’s “prickle of irritation.”

The way O’Farrell sets the Riordan family up, exploring in devastating detail the nature and origin of their internal dramas and their fractured emotions, provides the first, and most essential, of plot turns. Aoife is, in many ways, the catalyst of the story, a maddening yet compelling figure who swirls throughout these pages like a hurricane-force wind. It's not giving much away to say that she and Monica end up clashing, nor that their tempestuous interplay fuels a good deal of the narrative.

O’Farrell bestows a dangerous sense of insecurity on these people. This being a family saga, certain secrets are revealed at the holiday home in Ireland where they travel in search of Robert. The revelations turn Monica’s mind inside out in disbelief, and Gretta howls in despair for being too hard on her eldest daughter. The events strain Michael Francis’s marriage further, while the still-missing husband and his obsession with his past compounds to the suspect background of the entire family.

The author offers up a thought-provoking account of complex characters coming together in an unexpected ways. Beautifully written, the mystery revealed at the end illustrates the unknown territory of family life. Similar in tone and style to Anne Berry’s The Water Children (albeit without the psychological depth), Instructions for a Heatwave may not attain the richness of O’Farrell’s previous novels. Still, her evocation of sibling rivalry in all its careless, wrenching, essential, messy detail never fails to give pleasure.