Having conquered the movie world, Oscar winner Kevin Costner has embarked on a new venture – his first children’s novel.

“I leave the windows of opportunity in my life wide open,” he said of the debut novel, “The Explorers Guild: Volume One: A Passage to Shambhala,” which was released Oct. 20. It’s billed as an old-fashioned adventure story about a globe-trotting secret society investigating ancient legends.

But Costner, a double Academy Award winner for directing and producing 1990’s “Dances With Wolves,” said he didn’t write it just for fun or to entertain his three younger children.

“This is a business, too, and I think the book can be a popular stocking stuffer,” he said.

But Costner won’t need to wait until the holiday shopping season for big sales.

That’s because the 784-page epic cracked the New York Times bestseller list last week for hardcover fiction, coming in at No. 18.

Costner shares credit with his collaborators, co-writer Jon Baird and illustrator Rick Ross. All three live in the L.A. area. The book is published by Atria Books, a division of New York’s Simon and Schuster Inc.

“I knew I couldn’t do this by myself, so (I) needed a great team to work with,” said Costner, who spoke at a promotional event for the book in Santa Monica.

– Sandro Monetti