From the "Aboriginal Cult of Maria Lionza" to "Zoroastrianism" the four volume set "Religions of the World: A Comprehensive Encyclopedia of Beliefs and Practices" has information on every significant religion in the world. When it is a small local group with peculiar beliefs it is typically classified under "ethnoreligions". This is definitely appropriate as it would be impossible to chronicle every minor cult and sect of each religion. However, it covers the largest number of religions of any similarly titled book that I have seen. One of the things that make this series unique is the entry for each country. Besides having an entry for each religion it has each country listed along with a short religious history of the country and statistical information about the number of adherents of the various religions. For each religious group if there is a central address, web site, or other contact information it is listed. Associations are also listed as well as the history of the association and membership.The books are hard bound, contain copious photographs, and are of very high quality material and workmanship. All contributors are highly regarded professors, lecturers, and officers of the various religious groups or countries. This is another one of the items that make this set unusual, you are not getting one person's opinion of another person's beliefs but generally are getting the information directly from respected authorities within the religion or authorities on the religion. This is a very pleasant break from the all to common books today where, for example, a Christian is trying to explain Islam and doing so from an obviously slanted perspective. I would trust the information in this set of books to accurately portray the beliefs of the various religions in an unbiased manner more than just about any other book I have seen that professes to be a survey of various religions. The final point that makes this four book set unusual is the sheer number of religions examined. Most other books list twenty or thirty religions. In this set there are 135 entries just for the letter A. Professional, unbiased, informative, and thorough, it is the perfect set to own if you are interested in a basic understanding of the various religions of the world. "Religions of the World: A Comprehensive Encyclopedia of Beliefs and Practices" is a very highly recommended read.