Browsing the shelves for books is fun and useful, find the Library of Congress classification codes to browse by searching GIL Find, below are some examples for political science (LC classification uses letters, then numbers.)
JC Political theory. The State. Theories of the State. JC 131-273 the Modern State, JC 329 Patriotism
JF Political Institutions and public administration
JJ Political Institutions and public administration (North America)
JQ Political Institutions and public administration (Asia, Africa, Australia, Pacific Area)
JS Local Government JS 300-1583 United States
JV Colonies and colonization. Emigration and immigration. International migration.
JZ international Relations JZ 5511.2-6300 Promotion of Peace. Peaceful change.
F 281-295 Georgia local history