Nearly 40 years after Julie Andrews demonstrated a knack for helping “the medicine go down,” the star of the classic Disney film “Mary Poppins” is using her considerable rapport with children to convince them to swallow a different sort of chore: reading.

“It is so enormously gratifying at book signings whenever children do come up to me and say, ‘Thank you for getting me started on reading … you made me want to read more,’” said the film and singing legend, who also happens to be the author of 13 children’s books.

Andrews will join more than 80 authors, illustrators, storytellers, musicians and poets participating in the third annual National Book Festival organized by the Library of Congress and hosted by first lady Laura Bush this Saturday on the National Mall.

Although best known for her roles in “The Sound of Music,” “Victor/Victoria” and “Mary Poppins,” Andrews, who’ll celebrate her 68th birthday Wednesday, has been writing children’s books for more than three decades.

“I wrote my first book as the result of a bet that I lost to my eldest daughter,” recalled Andrews. “When I said, ‘OK, what’s my forfeit?’ She said, ‘Write me a book.’”

“Two years later the book [“Mandy”] was not only written but happily published,” Andrews noted.

Andrews, who writes her books under the name Julie Andrews Edwards in gratitude for the encouragement provided by her husband, director Blake Edwards, when she was struggling to complete “Mandy,” followed that book with perhaps her best-known work, the whimsical classic “The Last of the Really Great Whangdoodles.”

This month, she’ll launch her own HarperCollins Children’s Books imprint, “The Julie Andrews Collection,” which will publish four books: “Dumpy and the Firefighters” and “Simeon’s Gift” (co-authored by Andrews and her daughter Emma Walton Hamilton); “Grateful” by John Bucchino; and “Blue Wolf” by Catherine Creedon. Andrews is also putting the finishing touches on “Dragon,” a novel for young adults.

Though forced to give up her singing career after a 1997 operation damaged her vocal cords, Andrews remains involved in theater and film. This November she’ll start filming the sequel to her 2001 hit, “The Princess Diaries.”

“I think I’m one of those very fortunate women who has been asked to do a lot of things and is allowed to do a lot of things in this life and really the stimulation is swinging between them all,” said the upbeat Andrews, reflecting on her varied endeavors.

Andrews will appear Saturday with Bucchino and Creedon from 12:15 to 12:50 p.m. in the “Children” pavilion, where she will read and discuss her work. At 1:30 p.m., she’ll take part in a press conference for young reporters in the media tent and will also be on hand to sign books from 2 to 3 p.m.

In addition to Andrews, this year’s festival will feature a bevy of literary heavyweights including historian Michael Beschloss, writer Pat Conroy and “Master of the Senate” author Robert Caro, who will deliver the daylong event’s closing address at 5 p.m.

Throughout the day, authors will appear in theme pavilions that run the gamut from “History and Biography” to “Mysteries and Thrillers.”

The Library has added two new pavilions to this year’s lineup: a “Home and Family” pavilion, which will showcase authors of cooking and home improvement books, such as “Dare to Repair” co-author Stephanie Glakas-Tenet, wife of CIA Director George Tenet; and a “Poetry” pavilion, where more than a dozen poets, including National Endowment for the Arts Chairman Dana Gioia, will read from their works.

Attendees will also have the opportunity to vote for their favorite festival author on a 7-foot-tall Library Wall.

“We are subtly encouraging people to vote,” quipped Librarian of Congress James Billington.

Moreover, a Veterans History Project tent will be set up adjacent to the “History and Biography” pavilion to help generate interest and participation in what Billington deemed the LOC’s “biggest project” since the Depression.

“This is an attempt to get all veterans of wars from the whole 20th century,” Billington said of the undertaking.

Billington, who will be in Moscow along with first lady Bush this week to take part in a book festival hosted by Russia’s first lady, Lyudmila Putin, will lead an “intergenerational” reading session in the “Library of Congress” pavilion at 12:30 p.m.

Visitors to the LOC pavilion will also be able to take part in a book preservation clinic, receive information from the U.S. Copyright Office and consult experts about genealogy research, among other available resources.

A “Pavilion of the States” will feature information about literacy programs and resources from every state, the District of Columbia and U.S. territories.

As the festival has expanded so have its space requirements, Billington said. Organizers expect the event to draw more than 60,000 visitors, an increase of about 15,000 from last year’s attendance. In an effort to increase centralization, the festival — held last year on the Capitol’s West Lawn and part of the Mall — will run along the Mall from 14th Street to roughly the Smithsonian Castle, said Project Manager Roberta Stevens.

Some of the festival’s more than 600 volunteers will also be dispatched to three nearby Metro stops — Smithsonian (Mall exit), Archives-Navy Memorial and Federal Triangle — to distribute fliers, which include a map and schedule of events. More detailed programs will be available at the festival itself, Stevens said.

The National Book Festival runs from 10 a.m. to 5 p.m. rain or shine this Saturday on the National Mall. For a complete schedule of events, go to www.loc.gov/bookfest.