According to Brill, the EI includes "articles on distinguished Muslims of every age and land, on tribes and dynasties, on the crafts and sciences, on political and religious institutions, on the geography, ethnography, flora and fauna of the various countries and on the history, topography and monuments of the major towns and cities.

Most of the articles are signed, and while some are hardly more than dictionary entries, others are true research pieces – in many cases the best available treatment of their subject.This reference work is of fundamental importance on topics dealing with the geography, ethnography and biography of Muslim peoples.Historian Richard Eaton criticised the Encyclopaedia of Islam in the book India's Islamic Traditions, 711–1750, published in 2003.

Besides a great expansion in content, the second edition of EI differs from the first mainly in incorporating the work of scholars of Muslim and Middle Eastern background among its many hundreds of contributors: EI1 and SEI were produced almost entirely by European scholars, and they represent a specifically European interpretation of Islamic civilization.

The point is not that this interpretation is "wrong", but that the questions addressed in these volumes often differ sharply from those which Muslims have traditionally asked about themselves.

The persons do not represent the traditional learning of Qom and al-Azhar, to be sure; they have been trained in Western-style universities, and they share the methodology if not always the cultural values and attitudes of their Western colleagues.

The scope of EI3 includes comprehensive coverage of Islam in the twentieth century; expansion of geographical focus to include all areas where Islam has been or is a prominent or dominant aspect of society; attention to Muslim minorities all over the world; and full attention to social science as well as humanistic perspectives.