Lyman Frank Baum was an American writer of children's books. His most famous and popular book was "The Wonderful Wizard of Oz". Baum had to pay for the first Oz book himself, because no one wanted to publish it. But the first Oz book was a big success and children who read his books often wrote to Baum, and asked him to write more about Oz.
He tried to end it but his child readers kept demanding that he continue. He wrote 14 Oz books in all. The last two were printed after his death in 1919.