I don't know much about Lucy Thurber, the author of "Scarcity," which opened Thursday night at the Atlantic Theater Company. But I would guess her play is autobiographical. It's too aware of the emotional lives of poor people to be pure fiction.

The setting is a poverty pocket in the green hills of western Massachusetts, where the children in a damaged family yearn to escape.

Mom Martha, played with lively vulgarity by Kristen Johnston ("3rd Rock From the Sun"), works long hours at a mall shop. Dad Herb (Michael T. Weiss) is an alcoholic who doesn't work at all.

Their time together is spent smoking, drinking, swearing and having noisy sex whose sound echoes through their shabby house.

The kids, 16-year-old Billy (Jesse Eisenberg) and 11-year-old Rachel (Meredith Brandt), are super-bright, which is a blessing and a curse for them.

It's their means of getting away, but it will also separate them from their parents, and each other.

Thurber appreciates the push and pull of family life, the complexities that outsiders don't see. Probing beneath the stereotype of poor, uneducated, self-destructive people, she finds recognizable humanity.

In their coarse way, Martha and Herb love their kids, and Martha, in particular, is proud of their achievements.

Herb is an amiable drunk, not a violent one. He doesn't abuse his wife -- if he raised a hand to the strapping Martha, she'd probably knock his block off -- or his kids. They accept him, almost casually, as he is.

In a totally unexpected scene, Martha and Herb share a rare quiet talk amid the hurlyburly. They recall their youth, their wedding day, and how attractive and hopeful they were back then. (Herb is still handsome.)

Realizing this interlude will soon disappear into the messiness of their lives, Herb says, "Soon it will be like we never talked." Martha says, "I miss you more than you will ever know."

It's a lovely, sad, remarkably touching moment.

The children, particularly Billy, don't come into as clear a focus as their parents.

We're constantly reminded how smart Billy is, but we never quite see it. In Jesse Eisenberg's performance, he comes across as a run-of-the-mill sullen, unhappy teenager.

The intelligence, and maturity, of Rachel -- who I would imagine is the author as a girl -- is more persuasive, even as she eerily pursues a hobby of reading tarot cards. She's played winningly by Meredith Brandt, although the young actress doesn't always project her lines clearly.

With the arrival of the character who shakes up the household, the play unfortunately skids off the tracks.

Ellen (Maggie Kiley), an attractive, stylish young teacher, has taken a shine to Billy, and it's not because of his test scores. ("Do you know how rare it is to be sensual and intelligent?" she asks him. "God, you think such beautiful thoughts!")

The character, a rich, fancy, city lady, seems totally foreign to Thurber, who conveys little sense she knows how such a woman would speak or behave. Ellen seems to have been plucked from a titillating tabloid story.

She woos Billy -- who is much more sophisticated sexually than she is -- by helping him transfer, on full scholarship, to an elite prep school, all the while babbling away in stilted language that kept the audience laughing. ("I loved New York ... the city that never sleeps ... I've always wanted to work in education. My father's a law professor at Harvard. I had offers from some really fine prep schools, but I wanted to feel like I was making a difference, you know?")

The playwright obviously despises Ellen, and she might have conceived her as satire, but I don't think so.

Billy's departure means leaving Rachel, with whom he'd made a pact to stick together. That abandonment is emphasized at the end of the evening, but the playwright hasn't defined their relationship strongly enough to give the moment much emotional clout.

"Scarcity," vigorously directed by Jackson Gay, is extremely uneven. It does, however, offer a vital, sympathetic look at lives not often portrayed in the theater.