‘Mrs. Fletcher’ is a rare coming-of-middle-age story

“Mrs. Fletcher” takes a concept that sounds like a snooze and turns it into an unexpectedly absorbing limited series. Give much of the credit to “The Leftovers” producer-writer Tom Perrotta — adapting his book — and star Kathryn Hahn, who throws her all into a role distinguished by its lack of clear definition.

Hahn’s Eve Fletcher is proudly shipping her son off the college when the seven episodes begin, grappling — for the first time since her divorce — with an empty nest and the prospect of being truly alone. That leads her on what amounts to a journey of sexual self-discovery, one that includes watching a great deal of porn, albeit sheepishly.

Yet if Eve is struggling with what comes next, her son, Brendan (Jackson White), isn’t faring much better. A sort-of jerky frat-boy-type in high school, he has trouble finding his footing in college, where his swagger is frequently equated (correctly, much of the time) with arrogance. (Disney Channel star Cameron Boyce, who tragically died in July, plays his roommate, who sees through his bravado.)

Eve, meanwhile, works at a retirement home, where her declining patients offer a sobering preview of what’s on tap for, well, all of us, including one who — in the throes of dementia — has lost all his sexual inhibitions.

Eve also enrolls in a writing class, which brings her into contact with an assortment of characters — each with their own insecurities and issues — including Julian (Owen Teague), a shy high-school classmate of her son’s.

If there’s a rap on “Mrs. Fletcher,” it’s that the show idles a bit too much as it rather simply zeroes in on Eve and Brendan seeking to adapt to these new phases in their lives. Yet as over-the-top as some of the situations are, that sense of being lost, at any age, proves relatable, and Hahn perfectly captures her middle-aged confusion, often with little more than anguished expressions.

Granted, this is the kind of material that would have once been turned into an independent film, encompassing about half the time. The episodic structure allows for more development of the characters, but this is one of those exercises where knowing when to say “cut” is key.

Paired with the final season of “Silicon Valley” (not the most compatible duo, but never mind), “Mrs. Fletcher” arrives amid a wave of new HBO series with higher-profile titles and creative pedigrees, including “His Dark Materials” and “Watchmen,” produced by Perrotta’s “Leftovers” partner Damon Lindelof.

Somehow, it’s both the hardest to describe of that bunch, and the most effectively executed — a coming-of-age story, for once, that’s more about the parent than the kid.

“Mrs. Fletcher” premieres Oct. 27 at 10:30 p.m. on HBO.