The Grolier Encyclopedia of Knowledge, consisting of 6 hardcover volumes from 1991, is a comprehensive set covering a wide range of subject areas such as art history, natural science, human science, and history. Published by Grolier Incorporated in the United States, this encyclopedia series provides general knowledge and education on various topics including philosophy, architecture, military history, and political science. With a mix of abridged content and illustrations, this set is designed for intermediate level readers seeking a detailed exploration of various subjects in English language.