If you know the word or phrase you are looking for, try the Gazetteer: it's sorted alphabetically like an encyclopedia. Other entries are grouped thematically. For example, if you are looking for the entries on various countries, look under Civilizations. If you want to know more about languages, look under Communication, and so on. You'll need only one visit to the Introduction: it will tell you about the man who is responsible for creating this amazing compendium of lore.