The “New Book of Knowledge 1991” by Grolier Educational Staff is a comprehensive encyclopedia collection published by Scholastic Library Publishing. This hardcover set includes 21 books, making it a valuable resource for reference and learning. Written in English, this reference material covers a wide range of subjects and provides detailed information for readers of all ages. With its expert authorship and thorough content, this book set is a must-have for anyone seeking knowledge and information on various topics.