Photographs, drawings and other images provide information you can't always get from a text source. Images can provide details of everyday life such as clothing or material culture.
It is important to keep in mind that photographs are not an unbiased reflection of reality -- the photographer chooses what and how to depict a certain scene.
By using the subject heading: Pictorial works, you can find books on a topic that include or are primarily photographs. Go to the advanced search in the online catalog Search It and enter pictorial works as a subject and keywords for your topic.
Some examples:
Subject: Pictorial works
AND
Subject or Keyword: "Great Depression"
Subject: Pictorial works
AND
Subject or Keyword: "Soviet Union"