"How would you know that you time-traveled?" he asks.

It's only a fanciful musing but the two can't stop talking about the possibilities, so Perrin suggests they write a fantasy novel.

The re-enactment at Ardenwood Historical Farm was three years ago. Now the Berkeley technical writer, 46, along with daughters Hannah, now 12, and Tova, 14, are co-authors of their first book, "Time Like a River," and they have a contract on a second.

"It's kind of strange," Tova said. "Nobody believes you at first," that such a young person could have authored a published work. "It's a big accomplishment."

The Perrins' novel is about a teenager, who, while preparing for her bat mitzvah, discovers that her mother has contracted a life-threatening disease. The girl, Margie, travels through time to find a healer.

Coincidentally, Tova was preparing for her bat mitzvah while writing the book, which is set in the Perrins' Berkeley neighborhood.

Margie also goes to a public school named Willard, after Tova's own. But that's where the parallels end, the authors say — Tova and Hannah's mother is not dying, nor have the girls time-traveled.

They have, however, entered a world where few youths tread.

Tova recently hobnobbed with other authors at her first publishing cocktail party — accompanied by her mother. All three authors talk publicly to promote "Time Like a River." They even have advised a school district curriculum committee on how to group edit.

Their novel can be found in bookstores across the country — as well as in Canada, Australia and Europe.

"I've wanted to publish a book for a long time and fell in love with young-adult fiction," Perrin said, noting that there is a need for more kids' books with Jewish characters and themes.

He was inspired by some of his daughters' books, including "The Devil's Arithmetic" about a young girl who time-travels to the Holocaust and saves her own grandmother's life.

His daughters also see a need for more Jewish role models in contemporary literature. "It helps Jewish people feel part of a bigger community," Tova said.

The bookish troika brainstormed and fed off each others' ideas. Slowly, over the months, the story began to take form.

"I don't think any of us saw it as a book while we were working on it but all of a sudden it was a book," Hannah said.

Even Karen Tanner, the girls' mother, got involved with the project — if only for moral support.

Joked Perrin, "She thought I would get too enthusiastic and quit my day job."

With the story completed, Hannah says she now has the eye of an editor.

"I know exactly what to look for and how every single word affects a story. We're doing a lot of writing in school and it's really helping."

Perrin, who is the primary author, is sharing the profits 50-50 with his daughters. Tova is saving her money to go to Israel. Hannah said she simply likes having extra pocket change.

Neither of the girls contemplates a future publishing career, though Hannah says she wants to continue writing books on the side. She has begun the second Perrin family book with her father and is writing yet another on her own. It's about an African-American girl who struggles with racism and sexism to get on the neighborhood baseball team.