This is a great update from the 1995 edition. The book is divided into three main parts; all of them really interesting and engaging. In the first part, the author provides a theory of political parties. Why do we have political parties in democracies? According to the author, parties are endogenous institutions that help office-seeking politicians to get votes and solve various problems (the mobilization of voters, for example). In the second and third parts the author provides multiple evidence to test his theory (in fact, in these two parts, Aldrich demonstrates that he is a great political scientist: he writes clearly, he knows history and he dominates an array of methodological techniques). If you want to understand why parties form and how they dominate democratic politics, then this book is for you.