Magic Tree House 4: Pirates' Treasure!

Eight-year-old Jack and his little sister, Annie, are playing in the woods during their summer holiday, when they find a mysterious tree house full of books. But these are no ordinary books . . . And this is no ordinary tree house . . .
Jack and Annie are in a treasure trove full of trouble!
Stuck on a desert island, captured by the evil Captain Bones and his gang and a huge storm at sea . . . For a while, it looks like they might not get home safely after all. And they discover that their adventures are even more magical than they had first thought . . .

Mary Pope Osborne is the author of over forty books for young people, including novels, picture books, biographies, mysteries, and retellings of fairy tales and myths. She was the president of the Author's Guild, the leading organization for professional writers in the United States, for two years and has won many different awards for her books.
She lives in New York City with her husband, Will, and their Norfolk terrier, Bailey - who sleeps on the top of Mary's desk every day while she writes.