Often writers trying to inspire children to be creative will describe exactly how they became authors and urge them to follow in their footsteps.

Not Henry Clark.

Clark, whose second novel, "The Book That Proves Time Travel Happens" (Little, Brown, $17), hit shelves last week, is planning to tell the tweens and teens at Saturday's Authors Unlimited young-adult book festival at St. Joseph's College in Patchogue not to do what he did: "Don't wait until you're 59 to publish your first book."

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Clark, now 62 and from Bethpage, only started writing professionally after he left his job at Old Bethpage Village Restoration, where for 30 years he played the historical role of a 19th century phrenologist who examined the shape of and bumps on people's heads to determine their personalities. "It was different, certainly, but not what I wanted to do," he says. "I wanted to write in elementary school, in middle school and in high school."

Inspiring kids to keep picking up their pens -- or, in these days, tapping on their keys -- is the point of the fourth Authors Unlimited. Eight middle grade or young-adult authors will arrive in a limousine and walk a red carpet while the Long Island Ambassadors Drum and Bugle Corps plays. Authors will participate in a group panel discussion focused on the art of writing, and then kids will break into sessions with the different authors. Books will be available for purchase and signing.

Clark's book is about three modern kids who travel back to 1852, where they encounter slave traders and exploding steamboats and have trouble getting back to the 21st century. Here are three more of the eight authors who will be there:

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WHO Jason Reynolds

WHAT HE'S WRITTEN "The Boy in the Black Suit" (Simon & Schuster, $17.99), published in January, is the story of a young man who loses his mom to breast cancer. To deal with the grief, he takes a job at a funeral home and becomes a funeral crasher.

WHAT ELSE YOU SHOULD KNOW Reynolds, 31, lives in Bedford-Stuyvesant, Brooklyn. He grew up in Washington, D.C. His 2014 young-adult novel, "When I Was the Greatest" (Simon & Schuster, $17.99), won the Coretta Scott King/John Steptoe Award for New Talent among African-American authors. He was a featured artist on Beyoncé's website for Black History Month this year.

WHAT HE'LL TALK ABOUT Building characters. "The way I create characters is by creating entire back stories about people who don't exist," Reynolds says. They'll have families, personality strengths and weaknesses -- before Reynolds even starts writing the story. They'll go as far as having favorite foods and favorite colors, even if the reader never knows it.

WHO Elizabeth Kiem

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WHAT SHE'S WRITTEN "Dancer, Daughter, Traitor, Spy" in 2013 (Soho Teen, $9.99) and its 2014 sequel, "Hider, Seeker, Secret Keeper" (Soho Teen, $17.99) is about a family's three-generation feud with Russia's Bolshoi Ballet. She's working on the third book now.

WHAT ELSE YOU SHOULD KNOW Kiem, 44, has worked as a journalist for Reuters, NPR and CNN and lived in Russia after the collapse of the Soviet Union. She lives in Carroll Gardens, Brooklyn, and is moving to London this summer. She has a 15-year-old son named Henry.

WHAT SHE'LL TALK ABOUT Kiem says she plans "less of a craft talk and more of a topic talk." Her topics will likely include the era of the very late Cold War, which is when her books begin, and/or ballerinas behaving badly.

WHO George O'Connor

WHAT HE'S WRITTEN His seven-volume Olympian series of high-drama, comic book-style graphic novels is about Greek mythology. The most recent volume is 2015's "Ares: Bringer of War" (First Second, $9.95).

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WHAT ELSE YOU SHOULD KNOW O'Connor, 41, lives in Clinton Hill, Brooklyn, but grew up in Smithtown.

WHAT HE'LL TALK ABOUT The importance of research. "I'm going to talk about my process," O'Connor says. "Research and sketches, and the steps I go through as I create a graphic novel." He'll touch on his visits to Europe to see old Greek temples and will use a slideshow to illustrate his points.

The event

WHAT Authors Unlimited young-adult book festival for middle and high schoolers, but adults welcome

WHEN | WHERE 10 a.m. to 3 p.m. Saturday (doors open at 9:30 a.m.) at St. Joseph's College, 155 W. Roe Blvd., Patchogue

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INFO Free, but bring your own lunch or buy it in the St. Joseph's cafeteria; advance registration recommended; 631-286-1600, authorsunlimited.org