Readability, objectivity and style are the three important criteria of topics in encyclopaedias.
Readability: The topics covered by the encyclopaedia should be readable and easily comprehendable. The information must make the unfamiliar subject clear to the user. The standard and the quality of the articles should be in tune with the readers' need and should be comprehensible both for the scholars and layman.
Objectivity: The articles should be objective without having any national, political or religious bias. National encyclopaedias may deal extensively with the national topics but there should not be exaggeration. As far as possible, they should be neutral and not prejudiced.
Style: Encyclopaedias are meant for the diverse audience of different age group and coverage. They have different style. The scholarly style is for the learned scholars, popular style for the common men and the college students, easy, lucid and simple style for children. Hence, the reference librarian should be conscious in selecting encyclopaedias to suit the needs of the readers.