If Tracy Letts' "Superior Donuts" were actually a superior donut, it would be a chocolate-dipped old-fashioned — sweet, hearty and satisfying.

Best known as the Pulitzer Prize-winning author of "August: Osage County," an eviscerating look at the American family at its dysfunctional worst, Letts has a reputation for dragging his characters through darkness and horror in the name of drama. Look no further than the trailer-trash violence of "Killer Joe" or the psycho-terrors of "Bug" for evidence of that.

With "Superior Donuts," Letts lets in a little light.

The TheatreWorks production, now at the Mountain View Center for the Performing Arts, gives ample proof that when Letts wants to be funny or even conventional, he can do it with gritty, grin-inspiring dialogue that cuts through most of the sloppy sentiment.

Director Leslie Martinson is also TheatreWorks' casting director, so her advantage is the ability to hire some superior Bay Area actors and let them do their respective things under her guiding hand.

Howard Swain (a Letts veteran from Marin Theatre Company's hit production of "Killer Joe") plays Arthur Przybyszewski, son of Polish immigrants and proprietor of the family's crumbling donut shop in Chicago's Uptown neighborhood (the realistic set is by Tom Langguth and beautifully lit by Steven B. Mannshardt).

Alone in the world for various reasons, Arthur is a draft-dodging hippie now pushing 60. He's as decrepit as his shop, but behind the gray scruff and greasy ponytail is an incredibly bright, compassionate man who isn't quite done with the world, even as he tries to convince himself the world is done with him.

Arthur is so disconnected it takes him a while to even notice that vandals have trashed his donut shop and that two of his donut-loving police buddies are there to investigate. If Arthur can't bother to see the vulgarity spray-painted on his wall, there's absolutely no way he'll notice that the lady copy, Randy (Julia Brothers), harbors a giant crush on him.

Letts is playing with a sitcom format here, one that has fueled many a sappy "opposites clash and then change each other for the better" script, be it on film, TV or the stage. The opposite in this case is Franco Wicks (Lance Gardner), a 21-year-old "self-starter," as he describes himself when he bursts into the donut shop to apply for a job.

Before Arthur knows what's really going on, the kid has basically hired himself, and within a very short order, Franco is planning to spruce up the shop (and Arthur himself) for poetry readings. He might even make the donut relevant again.

Franco is a spirited young African-American and Arthur is a dispirited old white guy. They dispense with the issue of race when Franco asks Arthur if he's a racist. After a rambling answer that ends with, "I hope not," Arthur adds, "I hired you, didn't I?"

"Oh, scoot over, Mr. Lincoln," Franco retorts. "Make room on the penny."

But race isn't really the issue here. It's much more about hope — or the lack of it.

Franco, who has written the Great American Novel, is full of it. Arthur is devoid of it. What Arthur sees as fantasies, Franco sees as possibilities.

And because this is a conventional play — well written, perfectly performed, immaculately produced but conventional all the same— we will get to a happy ending. Bad things will happen — the worst is an offstage act of violence that made the opening-night audience gasp. And there will be onstage violence in the form of a fight between two men — Swain and Gabriel Marin as a money-grubbing goon — who have no business fighting but give their all with an assist from fight director Jonathan Rider's believable choreography.

Letts is not commenting on the conventionally well-made play or being ironic about it. He's simply making it work at a higher level than usual. If he set out to make a play that would make people feel good without making them feel guilty, he has succeeded mightily.

Swain and Gardner execute their cross-generation friendship beautifully, and we come to care tremendously for both Arthur and Franco and cheer for them both to come through their difficulties without losing the hope they've come to share.

The supporting cast is full of Bay Area greats including Joan Mankin as the crazy, drunk homeless lady who dispenses wisdom (did we mention this was conventional?). Brothers as the crushing cop is irresistibly sweet, especially when she's razzing her partner (Michael J. Asberry) for dressing up like a Klingon and going to "Star Trek" conventions.

Søren Oliver gets many of the evening's biggest laughs as Max, the Russian owner of a neighboring DVD store. Max has a big mouth and, it turns out, a similarly sized heart.

The well-made drama that doesn't aim to change the world is in short supply. This kind of show used to be the stock in trade of American drama, but in recent years, we tend to get extremes along the lines of ultra-silly comedies and hyper-sad dramas. The middle ground is infrequently trod. Warren Leight's "Side Man" and David Auburn's "Proof" are two middle-grounders that come to mind.

Letts' "Superior Donuts" is a welcome addition to this territory. The play, in its entertaining way, makes a modest but convincing case for the existence of hope in a cynical world. And there's certainly nothing wrong with that.

What: "Superior Donuts," a Tracy Letts play presented by TheatreWorks

Where: Mountain View Center for the Performing Arts, 500 Castro St.

When: Previews Oct. 8 at 8 p.m., with opening night Oct. 9 at 8 p.m. Runs through Oct. 31, Tuesday through Sunday.

Cost: Tickets are $19-$67.

Info: Go to http://theatreworks.org or call 650-463-1960.