There are entire online databases full of reference material. Take a look at these:
Encyclopedia of World Constitutions
K 3157 .E5 E53 2007 (Reference)
Arranged alphabetically by country, this 3-volume set provides the following information about each nation: constitutional history, basic organizational structure, leading constitutional principles, constitutional bodies, the election process, political parties, and fundamental rights.
Political Handbook of the World : Governments and Intergovernmental Organizations
JF 37 .P6 (Reference Desk Collection)
This book examines, in alphabetical order, the governmental organization and politics of each country in the world. Among the topics covered are political background, constitution and government, foreign relations, political parties, political movements, the legislature and cabinet, and the media.
Statesman's Yearbook : The Poliics, Cultures and Economies of the World
JA 51 .S7 (Reference Desk Collection)
Offers up-to-date snapshots of the countries of the world, including key historical events, population, climate, social statistics, constitution, government, recent elections, current administration, international relations, economy, industry, and trade.