The huge popularity of young-adult books like "The Hunger Games" series might leave the impression that children's literature needs no added promotion.

But librarians and reading advocates say children's books are constantly under pressure from other forms of entertainment like video games and television, a collective feeling that prompted the Library of Congress and other groups to form a new post in 2008 dedicated to promoting literature for children.

That position, the national ambassador for young people's literature, will be filled next by Kate DiCamillo, the author of "Because of Winn-Dixie" and "The Tale of Despereaux," the librarian of Congress, James H. Billington, is expected to announce on Thursday. A new ambassador is named every two years and makes appearances throughout the country to promote reading.

Ms. DiCamillo is already a star of the children's publishing world, a winner of the Newbery Medal and a reliable best seller. She writes fluidly across genres and age groups, from picture books to chapter books, experimenting with themes of loss, parental absence and spiritual redemption.

By her own account, she came to writing books in a meandering way. Born in Philadelphia but raised in Florida, she spent her 20s working jobs at Disney World, Circus World and a campground, harboring secret ambitions to be an author.

"I was in one of those terrible ruts," Ms. DiCamillo, now 49, said in a telephone interview from her home in Minneapolis. "I wanted to write, and I wasn't writing. And I finally decided that when I turned 30, I was going to write something."

One of her best friends was planning to move back to her hometown, Minneapolis. Ms. DiCamillo, feeling impulsive, decided to tag along.

"I had no winter coat and no job," she said. "I had turned 30, so I moved. It was the best thing I ever did."

Ms. DiCamillo took a job in a book warehouse there and spent her workdays as a "picker," sorting books — and reading them along the way.

Soon she mustered the courage to do her own writing. She began with short stories for adults — "thinking, in my misguided way, that because they were short, they were easier," she said — and then switched to children's books.

Within a month, she got the idea for her first book, "Because of Winn-Dixie," the story of a dog adopted by a lonely girl named Opal (Candlewick Press, 2000). Recognition, and more books, piled up quickly: Her second book, "The Tiger Rising," the story of children who band together to rescue an imprisoned tiger, received a nomination for the National Book Award. "The Tale of Despereaux" (2003), a fantasy novel about the hero's quest of a mouse named Despereaux Tilling, won the Newbery in 2004.

With a warm, lively personality and a boisterous laugh, Ms. DiCamillo would appear a natural fit for the post of ambassador, which asks for an ability to relate to children and an overall contribution to children's literature. She is the fourth person appointed to the position, following Jon Scieszka (2008), Katherine Paterson (2010) and Walter Dean Myers (2012).

Mr. Billington called Ms. DiCamillo a "worthy successor" in a statement. "Kate DiCamillo is not only one of our finest writers for young people," he said, "but also an outstanding advocate for the importance of reading."

The inauguration ceremony is scheduled for Jan. 10 at the Library of Congress in Washington. The initiative was founded by the Center for the Book in the Library of Congress, the Children's Book Council and its foundation, Every Child a Reader.

The Association of American Publishers, a trade group, said in November that sales of children's literature had decreased in the first eight months of the year — to $906.2 million in 2013 from $1.076 billion in 2012 — but that the decrease was largely attributable to the blockbuster sales of "The Hunger Games" books in 2012. Sales of children's books in the first eight months of 2013 were higher than in the same period of 2011.

Ms. DiCamillo is required to appear at the National Book Festival and at Children's Book Week in New York. Her message, she said, would be an inclusive one.

"It wasn't until my fifth or sixth book where I realized I'm trying to do the same thing in every story I tell, which is bring everybody together in the same room," Ms. DiCamillo said. "That's the same thing that I want here: to get as many different people into the room as I can. I don't know that I will resonate with a particular group of kids, but I want to get as many kids and as many adults together reading as I can."