Some denominations have much written about them. Others may have little research devoted to them. If you are finding little information on a particular denomination, try broadening your search to include a broader movement which encompasses your denomination (e.g., Pentecostalism, African-American Christianity).
When studying any denomination, it is important to find both "insider" information written by those within the denomination and "outsider" information written by those outside the denomination who may have a more nearly objective view.
OneSearch is a great place to start your research, as it combines most of the library's books, journal articles, and digital resources into a single search. Search OneSearch from the library website.
OneSearch Basics