“You’re trying to figure out, why the agita surrounding one normal day of white people problems?” Eleanor Flood says, launching into what looks like a run-of-the-mill story of a marriage in trouble, an artist stumped, sisters estranged.

What to do with all this oppressive normality? It’s a question that thrums through “Today Will Be Different,” as it did through Semple’s bestselling, strange and hilarious “Where’d You Go, Bernadette?” Eleanor, the artist behind a once fabulously popular animated series, “Looper Wash,” is stuck, fecklessly doing the wife and mother thing in Seattle while failing to produce her long-overdue memoir.

“Today will be different,” she vows, to begin with. “Today I will be present. . . . I’ll shower, get dressed in proper clothes and only change into yoga clothes for yoga, which today I will actually attend. . . . I will be my best self, the person I’m capable of being.”

It’s not much of a stretch to guess how this is going to work out. And sure enough, in the midst of her everyday concerns — avoiding a fraught lunch date, collecting her faux-sick son, Timby, from school, retraining her muddled middle-aged brain with poetry lessons — Eleanor discovers that her delightful husband, Joe, has been pretending to go to work all week. (Where is he?)

Today will be different, all right, but in an entirely different way than she planned.

Semple, who has written for the TV shows “Mad About You” and “Arrested Development,” has a singular genius for turning the ordinary inside-out and looking at it slantwise. While the mystery of Joe’s disappearance supplies the book with the somewhat shaky architecture of plot, all the in-between business keeps us happily occupied with its peculiar mash-up of the madcap and the poignant. Timby’s tummy ache, for instance, is brought on by “bullying”: a classmate “told me I bought my shirt at Target.” Eleanor’s dreaded lunch date is an untalented loser she once let go from “Looper Wash,” now a wildly successful artist with a show at the Seattle Sculpture Park.

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And the sculpture park, by lucky coincidence, is not only a clue to Joe’s whereabouts, it’s a great setting for knock-down, drag-out slapstick.

Plot may not be your favorite part of “Today Will Be Different,” especially when we finally find Joe. But meanwhile lunch with the erstwhile loser allows Semple to slip into third person to recount Eleanor’s history. At the heart of it all is “The Flood Girls,” Eleanor’s quirky illustrated rendering of her early family drama, which also has gone missing. The third-person section, which takes up a good chunk of the novel, mostly tells the story of what happened to separate Eleanor from her sister Ivy, and it’s a more conventional sort of narrative than the wisecracking, wryly self-aware play-by-play that frames it.

But the looser, loopier part of the novel is what’s most engaging about “Today Will Be Different.” Whether Eleanor is annotating a poem or navigating a Seahawks game or stalking her husband through the sculpture park, the allusions are quick and rich, the riffs nonstop and spot-on, and the results surprising.

“The ‘catatonic vision of frozen terror’ called these moments of existential doubt, or certainty, it was hard to know which,” Eleanor says, reflecting on the hard decisions ordinary people have to make on any given day. The wonder isn’t that so many novels take such moments as their subject. It’s that any of them are as good as this one.