It's the current edition complete with charts, maps, illustrations, facts, and figures.
Subject encyclopedias are another great resource.
In addition to an overview of a topic, subject encyclopedias usually include important terms, researchers in the field, and bibliographies of significant works. Subject encyclopedias are available in print format in the library. Book reviews can be located several ways. The first place to look is in the Book Review Digest . This database includes reviews from 1984 to the present.