Her lines draw on a slightly warped perspective

Roz Chast switched her focus to cartooning after graduating from RISD with a degree in painting.

The evidence of Roz Chast's success is everywhere. She has a two-page spread in the recent Cartoon Issue of The New Yorker magazine, a publication to which she has contributed regularly since 1978. "The Alphabet from A to Y, with Bonus Letter Z!" written by Steve Martin and illustrated by Chast, is number five on The New York Times best-seller list for children's books. And fans will no doubt line up Tuesday at her Brattle Theatre appearance to ask about their favorite of her drawings from various magazine and books.

But Chast still doesn't feel like she's made it. She has never looked at The New Yorker's online shopping page with Chast-related sweatshirts and mugs, and she still has a freelancer's fear that she won't have anything to turn in next week and work will dry up.

What would make her finally feel secure? "A brain transplant?" she says. "I don't really know."

When Chast graduated from the Rhode Island School of Design with a degree in painting in 1977, there was no clear career path for her to follow. She had wanted to draw since she was a child, watching Betty Boop cartoons and reading Charles Addams and Mad magazine. She briefly considered a career as an illustrator, but her heart wasn't in it, and she quickly switched her focus to cartooning.

"You have to really want to do this," she says. "You have to feel like maybe it's the only thing you can do and if you didn't do it, things would really be much, much, much, much worse."

There is a subtle friction in much of Chast's work, an uneasiness with ordinary life. One cartoon, titled "Cruises to Nowhere," depicts "A visit with Aunt Zelda," "A tete-a-tete with Mathilda," and "A luncheon date with Victor." In each frame, the subjects look happy in their natural settings, but Chast gives you the feeling you're trapped with them - a claustrophobic sense of normality.

"I don't want to write gags," she says. "It's not something I'm interested in. I would rather find something that really genuinely amused me, that made me laugh, that you'd tell a friend, 'Oh, you've got to see this.' "

Although the slightly warped perspective and gently curving lines of her art are distinct, Chast doesn't have a signature format, like Gary Larson's one-frame "Far Side" or R. Crumb's storyboards. She is free to tailor her cartoons to her thoughts, whether that's a single phrase or a short narrative. "The New Yorker has allowed me to do that, and I'm grateful," she says. "I'd get kind of bored. I really think a cartoon should be allowed to be what it wants to be."

That can also mean popular books like "The Party After You Left" or the new "Alphabet" book with Martin, whose absurdist sense of humor is a perfect match for her art. "When I saw this book," she says, "I thought, 'This is going to be fun,' because I think these things will really complement each other."

And yet, Chast is still somewhat surprised when her work connects. "It's just amazing that anybody finds the same things funny that I find funny," she says.

Around Town

Bill Braudis drops by the Comedy Studio tonight. D.L. Hughley is at the Comedy Connection tonight and tomorrow. A troupe of actors will perform for 24 hours at Improv Asylum starting tomorrow night at 10 to benefit Globe Santa.