The "Mystery of the Flying Express" is a hardcover book from the Hardy Boys series, written by Franklin W. Dixon. Published by Grosset & Dunlap in 1970, this English-language novel is set in North America and is part of the children's mystery genre. The story revolves around the Hardy Boys, a character family known for solving intriguing mysteries. This book, with its hardcover binding, is a collector's item for fans of the Hardy Boys series and children who enjoy engaging mystery stories. Perfect unopened condition.