In the 1960s, these encyclopedias were a good place to look for an overview of a subject to be used in a research paper. Even now, they are useful for understanding the earlier history of subjects such as the Cold War, the Civil Rights Movement, biographies of people who are deceased already, and the early history of computers. They are easy to understand, factual for their time, and useful as a starting point. Plus, dinosaurs and volcanoes don't change much and kids like to read about them over and over again. They are complete with good covers and bindings and all of the pages and illustrations are clear and unmarked.