This is a set of 11 books from The Hardy Boys series, written by Franklin W. Dixon and published by Grosset & Dunlap. The series follows the adventures of amateur detectives Frank and Joe Hardy. In “The Secret of the Old Mill,” the brothers work to uncover the mystery of a counterfeiting ring, while in “Hunting for Hidden Gold,” they search for a missing treasure. The set is in very good condition, with some volumes showing signs of wear and age, such as slight rubbing on the covers and signatures on the inside pages. Despite this, the books are clean, tightly bound, and mostly free of markings, making them a valuable addition to any collection of classic children’s literature.