As you are starting to explore a new research topic, reference sources are a good way to gain background information on your topic. High quality, academic, multivolume sets, will often give you the beginnings of scholarly research on a subject by providing a short bibliography of important works on the subject.
Even with advanced subject knowledge of an area, you will run across unfamiliar people, places and events. Library reference sources will allow you to quickly fill in those gaps and improve your contextual knowledge with more reliability than a Wikipedia article.
To search for additional reference books, do an Advanced Search in HopeCat. Enter a general keyword on your topic and choose "Van Wylen Reference" as the location.