To locate books, try GW Library Search - Advanced Search using the term sociology. Add other search terms in the additional search boxes that relate to your topic. More specific examples might include:
Books on sociology may be found in these call number ranges:
HM: General Sociology
HN: Social History & Problems
HQ: Women, Family
HT: Communities, Classes, Races
HV: Social pathology, Public Welfare, Criminology
Books in these ranges are located on the 5th floor of Gelman. See the "Gelman Stacks Map" to the left.