Written by leading specialists in political science on the subject, this book critically examines key concepts, approaches and approaches that are currently circulating on political parties. Its authors review the trials often formulated their functions, typologies and trends in democratic systems. Through a clever combination of theoretical and empirical chapters, crises and experienced by Western parties changes are discussed, considering their organizational models and discusses some of the paradoxes and contradictions that are the subject. The book also contains several chapters devoted specifically to explore these issues in the Spanish parties. The result is essential to assess the role of parties in contemporary democracies work.