Most Sociology and Social Work materials fall into the followoing call number ranges:
300-301 (Sociology)
360-363 (Social Work)
Additionally, you may be interested in social science reserach methods, wich may be found in the following range:
300-301
It's usually best to start with a keyword search, but subject headings applied to relevant books can help to refine your results. Open the item record of a book that interests you. Scroll down to the clickable subject headings, and run another search to explore similar books.
You can also browse the headings associated with a particular topic as a way of getting started with your research.
Trust by 
Achieving Competence Social Work Field by 
Foundations of Interpersonal Practice in Social Work by 
Contemporary Sociological Theory and Its Classical Roots by 
The Handbook of Qualitative Research by 
Investigating the Social World by 
Macro Practice in Social Work for the 21st Century by 
Salsa Dancing into the Social Sciences by 
Sociology : a brief introduction by 
Solution-Oriented Social Work Practice by 
Women in Social Work Who Have Changed the World by 