The new novel from Lionel Shriver, "Should We Stay or Should We Go," starts out seeming rather claustrophobic and grim.

In Chapter 1, we meet a British couple named Cyril and Kay Wilkinson, both just past 50, he a doctor, she a nurse. Having just buried Kay's dad at the end of a miserable period of dementia and dependency, they want to spare their three children, the national health system, and themselves similar trials. Cyril suggests a suicide pact. When Kay turns 80, one year after Cyril does, they will off themselves. Neatly, with pills. They'll put their affairs in order and quit while they're ahead.

Kay calculates that it will then be 2020. 2020?! A "ridiculous year, an unfathomable year, the stuff of late-night films with spaceships and dying suns" — well, she blithely assumes, it will never arrive.

Sorry, Kay, but the second chapter opens in 2019. Cyril is in a fury about Brexit and Kay is feeling deep doubts about their agreement. She's having a very nice life with no serious health issues or complaints. Must it end? Having lost interest in most activities — why watch a documentary about the loss of biodiversity in the Amazon when she certainly won't be around for the extinction of the white-cheeked spider monkey? — she becomes obsessed with planning their memorial service, making play­lists, composing numerous farewells and voluminous explanations.

By now, the reader, too, is having doubts. How is this going to go on for another 200-some pages?

Especially since Cyril and Kay come to their ends, though not exactly as planned, by page 70.

At this point Shriver opens her bag of tricks. Chapter 3 starts over from a certain point in the couple's last evening, and moves to a different version of their deaths. Chapter 4 is titled "Cyril Has an Unexpected Change of Heart." It, too, begins at the 11th hour, but follows a very different road.

Chapter 5 starts back in 1991, and by now the game is really on. Assisted living, Alzheimer's, mental institutions, immortality drugs, cryogenics laboratories, and what it would be like in a truly perfect world are all on the agenda. The pandemic makes an appearance every time 2020 arrives, Brexit and mass migration wander in and out, and with many stories continuing to 2021 and beyond, different futures are explored.

As in her 2007 bestseller, "The Post-Birthday World," Shriver uses the gambit of alternate narratives to explore her characters and the possibilities of love. In different scenarios, with different choices, Cyril and Kay become more passionate, or more distant; the balance of power in the relationship shifts, and shifts again. One point Shriver seems to be making is that people can still change and grow after 50, after 60, and after 80, too.

It seems that if we can, we should stay.

Marion Winik is a book critic in Baltimore and a board member of the National Book Critics Circle.

Should We Stay or Should We Go

By: Lionel Shriver.

Publisher: Harper, 288 pages, $26.99.