Anna Dewdney, whose “Llama Llama” read-aloud picture books amused and comforted millions of preschool children, died on Saturday at her home in Lower Bartonsville, Vt. She was 50.

The cause was brain cancer, her sister the anthropologist T. M. Luhrmann said.

Ms. Dewdney, whom the children’s-book journal The Horn Book once called a “rock star to preschoolers,” introduced her most famous character in “Llama Llama Red Pajama.” Published in 2005, it told the rhyming story of a baby-boy llama upset when his mother delays bringing a nighttime glass of water. Mama eventually turns up and the crisis is averted. Baby llama learns that Mama will always be nearby.

Parents and children loved the book. “Dewdney gives a wonderfully fresh twist to a familiar nighttime ritual,” Booklist wrote.

Booksellers loved it, too. The title flew off the shelves, as did its nearly 20 successors, which sold more than 10 million copies. Netflix plans to offer an animated version of the books next year.