In a much-memed scene from the second season of “Fleabag,” the protagonist is in the middle of confession with her hot priest crush and divulges a flash of what feels like genuine, abject self-discovery. “I just think I want someone to tell me how to live my life,” she says. Now picture the Father is replaced by a Mother (or, better yet, a Mommy), the confessional by a cellphone screen in a Brooklyn apartment, the 30-something British antihero by a 20-something Jewish American woman, and you can begin to imagine the essence of Alexandra Tanner’s fabulously revealing debut novel, “Worry.”

Jules is a 28-year-old aspiring writer from Florida with an M.F.A. in fiction and a day job at a website that sells study guides of classic novels. In claustrophobic present tense she candidly narrates the minutiae of her fixations, disappointments, aversions and maladjustments as she navigates adulthood.

At the risk of being too schematic, Jules’ interests, beyond her efforts to achieve literary renown, can be boiled down to consuming “Christian Mommy” social media content and critiquing her sister, Poppy. The former is symptomatic of a larger personal complex — though Jules wants to be independent, she craves a matriarchal authority’s approval, guidance and comfort, perhaps because her own mother can be rejecting and inscrutable. In its more superficial manifestation, Jules’ curiosity consists of scrolling the internet for hours each day, watching Instagram moms share conspiracy theories in all-caps and hawk products.

Poppy, younger than Jules by a few years, is following in her sister’s footsteps. Having just emerged from a rocky early 20s, marked by short-lived professional prospects and mental health crises, she moves into Jules’ spare room, begins working jobs similar to her sister’s and also starts an entertainment binge, watching episodes of “Sailor Moon” with Jules. Poppy suffers from chronic outbreaks of hives. Like Jules, she is often overwhelmed and fearful of the world, although compared with her sister she seems more secure in her own mind, if not in her own skin. In a moment of self-love, Poppy adopts a three-legged dog named Amy Klobuchar.

Tanner works wonders with little character development (I’d call it “character entrenchment”) and hardly any plot (eventually, Jules and Poppy go to Florida for Thanksgiving), trusting humor to structure the story all the way through.

The novel runs on an engine that relentlessly converts suffering, usually of the inner-turmoil variety, into comedic relief.

Speaking from experience, “Worry” also nails what it was like to be a youngish media worker in Brooklyn in 2019 — desperate for meaningful success in a crumbling industry, addicted to the fleeting dopamine hits of social media, online shopping and clicking “send” on grant applications. It’s funnier than it should be. There’s reading tweet threads about Caroline Calloway and going to see a terrible adaptation of a Greek tragedy that knowingly references Uber. There’s “Cali sober” and envisioning “buying this one really ugly dress from Rachel Comey.” These details inspire a potent mixture of familiarity and shame, like one of those compilations of photos your phone shows you about meals you just ate.

In another aggressively 2019 moment, Jules decides to interview for a job writing horoscope content for an astrology app. Jules’s interviewer, another would-be writer, asks her what getting an M.F.A. was like. She considers being brutally honest, saying: “There’s not much to tell about my M.F.A. Mostly I remember going to dark bars and magazine parties after class to try to meet nasty editors and glimpse obscure literary celebrities.”

In the end, Jules responds with a dash of generic writing advice packaged in a more optimistic anecdote, which never really happened, at least not to her. Some stories give you the unvarnished truth, some the varnished one. “Worry” is generous and wise enough to give both.